Lung Cancer: Understanding Your Pathology Report After Surgery

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Lung cancer starts in lung tissue. Most lung cancers begin in the cells that line the airways. Others begin in the cells lining the tiny air sacs where oxygen passes into the blood. As a lung cancer grows, it can invade surrounding lung tissue and reach the lung surface. It can also spread to nearby lymph nodes. Less often, it travels to other parts of the body. That is called metastasis.

This article explains the pathology report created after surgery to remove a lung tumor. The operation may be called a wedge resection, segmentectomy, lobectomy, or pneumonectomy.

Why your pathology report looks like a checklist

Most lung cancer pathology reports include a section that looks like a list of headings, each followed by a short answer. This is called a synoptic report. It follows a standard checklist published by the College of American Pathologists (CAP). Laboratories across North America, Europe, and much of the world use the same one. The checklist makes sure that every feature known to affect treatment is reported for every patient, in the same words, no matter which laboratory examined the tissue.

One checklist covers three different groups of lung tumor. The first is non-small cell lung cancer, which includes adenocarcinoma and squamous cell carcinoma. The second is small cell carcinoma. The third is carcinoid tumors, which grow slowly. Many patients would not think of a carcinoid tumor as lung cancer at all.

Small cell carcinoma and carcinoid tumors both start in neuroendocrine cells. These hormone-producing cells are scattered throughout the airway lining. Non-small cell lung cancer does not start in these cells.

Because one checklist covers all of these tumors, your report may list items that do not apply to your situation. An item asking about the bronchus will not apply if your operation removed only a wedge of the outer lung. An item asking about growth patterns applies only to one family of adenocarcinomas. When an item does not apply, the report will say something like “not identified,” “not applicable,” or “cannot be determined.” Seeing those phrases does not mean something was missed. It usually means the feature was looked for and was not there, or that the tissue removed did not include the structure being asked about.

This checklist is used for cancer removed by an operation. A small biopsy taken through a bronchoscope or a needle is reported differently, and so are fluid samples drawn from around the lung. Mesothelioma, lymphoma, and sarcoma each have their own checklist, so a report on one of those will not match the items described here. Biomarker results are reported on their own separate checklist, described near the end of this article.

This article covers every item on the checklist, in the order you will find them on your report. Reading it will help you understand what each term means and why it matters for your care.

How is the diagnosis made?

A pathologist diagnoses lung cancer by examining a tissue sample under a microscope. In most cases, a CT scan first shows an abnormality. They then sample it with a biopsy, either through a bronchoscope passed down the airway or with a needle passed through the chest wall. Some small tumors are removed surgically without a biopsy first, and the diagnosis is made from tissue taken in the operating room. The report described in this article comes from the tissue removed at surgery.

Under the microscope, the pathologist looks for cancer cells growing where they do not belong. The pathologist then works out which normal structure those cells most resemble, because that determines the type of lung cancer. Cells forming glands or producing mucus suggest adenocarcinoma. Cells that are flat and packed together, sometimes making keratin, point to a squamous cell carcinoma. Small cells with almost no cytoplasm that mold against one another suggest small cell carcinoma. In an adenocarcinoma, the pathologist also decides whether the tumor has truly invaded. Invasion means the tumor has grown into the lung’s supporting tissue. Some lung adenocarcinomas instead spread along the walls of the air sacs and leave those walls intact, which is not counted as invasion.

When the appearance alone is not enough, the pathologist performs immunohistochemistry, a test that uses colored stains to show specific proteins in tissue. A stain for TTF-1, often together with napsin A, supports adenocarcinoma arising in the lung. Stains for p40 and p63 support squamous cell carcinoma. Stains for synaptophysin, chromogranin, and INSM1 confirm a neuroendocrine tumor, and Ki-67 helps separate a slow-growing carcinoid tumor from a fast-growing neuroendocrine carcinoma. If your pathologist suspects that the cancer in the lung may have started somewhere else, a broader panel of stains is used to find its origin. After lung cancer is confirmed, imaging assesses how far the disease has spread. This usually means a CT scan of the chest and abdomen, a PET scan, and an MRI of the brain. The pathology report describes what was found in the removed tissue; imaging describes the rest of the body.

The operation and which lung the tissue came from

The first items on a lung cancer pathology report describe the specimen, meaning the tissue sent to the laboratory. They also state which side of the chest it came from. The right lung has three lobes, and the left has two. Surgeons remove as little lung as the tumor allows while still clearing it completely.

Wedge resection — Removal of a wedge-shaped piece of lung containing the tumor, without following the natural divisions of the lung. The cut edge is closed with a row of staples.
Segmentectomy — Removal of one anatomic segment of a lobe, along with its own airway and blood vessels. For small tumors, this and wedge resection are together called limited or sublobar resection.
Lobectomy — Removal of one whole lobe. This is the most common operation for lung cancer.
Completion lobectomy — Removal of the rest of a lobe from which tissue was already taken at an earlier operation.
Sleeve lobectomy — Removal of a lobe together with a section of the airway serving it. The remaining airway is then rejoined, so the other lobes on that side can be kept.
Bilobectomy — Removal of two lobes, possible only on the right side.
Pneumonectomy — Removal of an entire lung.
Major airway resection or adjacent structures — Part of a large airway removed with the lung. It may also mean a neighboring structure, such as the chest wall or pericardium, taken because the tumor reached it. The report names what was included.
Specimen laterality — Whether the tissue came from the right lung or the left. Reports may say “not specified” when the request form did not state it.

Synchronous tumors: separate cancers found at the same time

When a lung operation removes more than one tumor, the pathologist must decide what the extra tumors represent. They may be separate cancers that arose independently. They may instead be one cancer that has already spread within the lung. The difference matters. Two separate cancers are staged separately, and this is usually less concerning than one cancer that has spread.

Pathologists decide based on how the tumors look under the microscope. Tumors of clearly different types, such as one squamous cell carcinoma and one adenocarcinoma, are separate primary cancers. Pathologists compare adenocarcinomas in detail, pattern by pattern, and treat tumors that differ as separate primaries. When the report says synchronous tumors are present, it gives the total number of primary tumors and the identifying number of each specimen. A separate synoptic report is usually issued for each cancer. That is why you may have received more than one report from a single operation.

Tumor focality: one tumor or more than one

Focality describes how many separate areas of lung cancer were found and where they sit relative to one another. Unlike the item above, this one covers tumors judged to be related to the main cancer, and each answer carries its own stage.

Single focus — One tumor. This is the most common answer.
Separate tumor nodules in the same lobe — Additional nodules of the same cancer in the lobe containing the main tumor. This makes the tumor stage pT3 regardless of size.
Separate tumor nodules in a different lobe on the same side — Additional nodules in another lobe of the same lung. This makes the tumor stage pT4.
Separate tumor nodules in a lobe on the opposite side — Additional nodules in the other lung. This is classified as distant spread, pM1a.
Multifocal tumor nodules of similar type — Several nodules, often faint hazy spots on the CT scan called ground-glass nodules. These are best understood as separate slow-growing cancers rather than as spread, and there are frequently too many to report one by one. The stage is based on the largest nodule. The letter “m” in brackets, or the number of nodules, is added to show that there were several.
Pneumonic-type adenocarcinoma — A form that spreads diffusely through a region of lung and looks on imaging like pneumonia rather than a lump. It is staged by how many lobes it involves rather than by measurement.
Cannot be determined — The pattern could not be established.

Tumor site: where in the lung the cancer started

Tumor site names the part of the lung the cancer arose in. The pathologist selects every site the tumor involves, so a large cancer may have more than one name. The choices are:

Upper, middle, or lower lobe of lung — The right lung has all three. The left lung has only an upper and a lower lobe.
Main bronchus — The large airway entering each lung.
Bronchus intermedius — A short segment of airway on the right side only.
Lobar bronchus — The branch of airway serving one lobe. The report names which.
Other, or not specified — A site that does not match those above, or one the request form did not state.

Where a lung cancer sits shapes what the surgery had to remove. It also shapes which of the remaining items apply. A tumor at the outer edge of the lung is close to the pleura, the smooth membrane covering the lung surface, so pleural invasion becomes important. A tumor in a large central airway is close to the bronchial margin and may block the airway behind it. That is why the checklist asks about atelectasis (collapsed lung) and obstructive pneumonitis (inflammation behind a blockage).

Tumor size

Tumor size is the largest measurement of the lung cancer, given in centimeters, and your report may add a second and third measurement. Size is one of the two main factors determining the tumor stage, along with what the tumor has grown into. If the tumor could not be measured, the report says “cannot be determined” and explains why.

For most types of lung cancer, one number covers it. Adenocarcinomas that grow partly along the walls of the air sacs are the exception. This is the item on the report that most often confuses patients, because it produces two different sizes for one tumor.

Invasive tumor size — The measurement of the part of the tumor that has genuinely invaded, meaning any part that is not simply growing along intact air sac walls. For every type of lung cancer other than a non-mucinous adenocarcinoma with a lepidic component, this equals the whole tumor.
Total tumor size — Reported in addition when a non-mucinous adenocarcinoma has a lepidic component. Lepidic means an area where the tumor cells creep along the walls of the air sacs without destroying them. This measurement includes both the invasive and the lepidic parts.
Percentage of the total that is invasive — Given when the invasive areas are scattered rather than forming one measurable lump. The pathologist estimates the proportion and multiplies it by the total size.
Size of in situ carcinoma — Reported when the tumor has not invaded at all.

Staging is based on invasive size alone, not total size. This is why a report may describe a 3-centimeter tumor and still assign a low tumor stage. If only 8 millimeters of that 3 centimeters is invasive, the stage follows the 8 millimeters. Both numbers are reported because the rule is still being studied, and researchers need the pair.

Types of lung cancer (histologic type)

Histologic type describes what the lung cancer looks like under the microscope and which normal structure it most resembles. Pathologists assign the type using the World Health Organization (WHO) classification of thoracic tumors. Type matters more in lung cancer than in most other organs. It determines which chemotherapy drugs are suitable and which biomarker tests are performed. For small cell carcinoma, it also determines whether surgery is part of treatment.

Adenocarcinoma

Adenocarcinoma is the most common type of lung cancer, accounting for roughly 40 out of every 100 cases and for most lung cancers in people who have never smoked. It develops from the gland-forming cells lining the small airways and air sacs, and it usually arises toward the outer part of the lung. The checklist names several forms, which differ mainly in how far the tumor has invaded and whether the cells produce mucus.

Adenocarcinoma in situ — A tumor 3 centimeters or smaller in which the cells grow purely along intact air sac walls with no invasion at all. It is staged as pTis and is cured by removal.
Minimally invasive adenocarcinoma — A tumor 3 centimeters or smaller, mostly growing along air sac walls, with an invasive area of 5 millimeters or less. Vessel invasion, pleural invasion, and necrosis must all be absent. It is staged as pT1mi and outcomes are excellent.
Invasive lepidic adenocarcinoma — Growth predominantly along air sac walls, with more invasion than minimally invasive adenocarcinoma allows. This form carries the most favorable outlook among the invasive adenocarcinomas.
Invasive acinar adenocarcinoma — The tumor forms rounded glands. This is the most common form.
Invasive papillary adenocarcinoma — The tumor forms finger-like fronds with a core of supporting tissue.
Invasive micropapillary adenocarcinoma — Small tufts of tumor cells with no supporting core, often floating free in spaces. This form is associated with earlier spread to lymph nodes.
Invasive solid adenocarcinoma — Sheets of tumor cells forming no glands. Immunohistochemistry or a mucin stain is often needed to confirm that the tumor is an adenocarcinoma.
Invasive mucinous adenocarcinoma — The tumor cells are filled with mucus. This form often grows along air sac walls but is measured as a whole rather than by its invasive part, and it is more often multifocal or pneumonic in pattern.
Mixed invasive mucinous and non-mucinous adenocarcinoma — Both patterns are present in meaningful amounts.
Colloid adenocarcinoma — Tumor cells float in large pools of mucus that replace the air sacs.
Fetal adenocarcinoma — The glands resemble developing fetal lung. The low-grade form occurs in younger patients and carries a favorable outlook.
Enteric-type adenocarcinoma — The tumor resembles a colon cancer under the microscope. Before this diagnosis is made, spread from an actual colon cancer has to be excluded.

Squamous cell carcinoma

Squamous cell carcinoma is the second most common type of lung cancer, accounting for roughly 25 to 30 out of every 100 cases, and it is strongly associated with smoking. It develops from flat squamous cells that replace the normal airway lining after years of injury. These tumors therefore arise more often in the central lung, near the large airways. The checklist names four forms.

Squamous cell carcinoma in situ — Abnormal squamous cells fill the full thickness of the airway lining but have not broken through into the tissue beneath. It is staged as pTis.
Invasive keratinizing squamous cell carcinoma — The tumor cells make keratin, the tough protein found in skin and hair, visible under the microscope as pink whorls.
Invasive non-keratinizing squamous cell carcinoma — No keratin is produced, so immunohistochemistry is used to confirm the squamous type.
Invasive basaloid squamous cell carcinoma — The tumor cells are small and densely packed with little cytoplasm, resembling the basal layer of the airway lining. This form tends to grow faster than the others.

Small cell carcinoma

Small cell carcinoma accounts for roughly 13 to 15 out of every 100 lung cancers and is very strongly associated with smoking. Under the microscope, the tumor is made of small cells with very little cytoplasm, nuclei that mold against one another, and many dividing cells. It grows and spreads faster than the other types. For that reason, it is usually treated with chemotherapy and radiation rather than surgery. Only a small proportion of patients with small cell carcinoma have a resection specimen. When surgery is performed, it is generally for a small tumor found before spread was suspected.

Your report may say combined small cell carcinoma, which means a non-small cell component, such as adenocarcinoma or squamous cell carcinoma, is also present. The report names that other component.

Carcinoid tumors and large cell neuroendocrine carcinoma

Neuroendocrine tumors of the lung arise from hormone-producing cells scattered through the airway lining, and they span a very wide range of behavior. All of them are covered by this checklist, so a patient with a slow-growing carcinoid tumor and a patient with a fast-growing neuroendocrine carcinoma receive reports that look the same.

Typical carcinoid, also called neuroendocrine tumor grade 1 — Fewer than 2 dividing cells in a measured area and no necrosis, meaning no areas of dead tumor cells. These grow slowly, are often found in younger patients, and are frequently unrelated to smoking. Most are cured by surgery.
Atypical carcinoid, also called neuroendocrine tumor grade 2 — Between 2 and 10 dividing cells in that same area, or any necrosis. These behave less predictably than typical carcinoids and more often reach lymph nodes.
Carcinoid tumor, not otherwise specified — The tumor is a carcinoid, but the tissue available did not allow the distinction between typical and atypical to be made.
Large cell neuroendocrine carcinoma — A fast-growing neuroendocrine carcinoma made of larger cells, with a high number of dividing cells and extensive necrosis. It sits alongside small cell carcinoma rather than alongside the carcinoids, and it is treated similarly.
Combined large cell neuroendocrine carcinoma — The same tumor with an additional non-small cell component, which the report names.

Other and rare types

Together, the remaining types account for a small share of lung cancers. Each is named on the checklist so that a patient with an uncommon diagnosis can find it.

Large cell carcinoma — A carcinoma that shows no gland formation, no squamous features, and no neuroendocrine features. Its immunohistochemistry does not point in any direction either. This diagnosis can be made only on a resection specimen, because the whole tumor must be examined before you can say no defining feature exists.
Adenosquamous carcinoma — Both adenocarcinoma and squamous cell carcinoma are present, each making up at least 10 percent of the tumor.
Pleomorphic carcinoma — A carcinoma containing at least 10 percent spindle-shaped cells, giant cells, or both. The report lists the components present and may give the percentage of each.
Pulmonary blastoma — A rare tumor with a fetal-type gland component and a primitive supporting-tissue component. The report gives the percentage of each.
Carcinosarcoma — A carcinoma combined with a sarcoma component such as bone, cartilage, or muscle. The report names and quantifies both parts.
NUT carcinoma — A rare fast-growing cancer defined by a specific gene fusion involving the NUTM1 gene. It occurs in younger patients and is confirmed by a stain for the NUT protein.
Thoracic SMARCA4-deficient undifferentiated tumor — A rare tumor defined by loss of the SMARCA4 protein, which normally helps control which genes a cell switches on.
Lymphoepithelial carcinoma — A carcinoma surrounded by dense sheets of immune cells. In the lung it is often associated with Epstein-Barr virus.
Adenoid cystic carcinoma, epithelial-myoepithelial carcinoma, mucoepidermoid carcinoma, hyalinizing clear cell carcinoma, and myoepithelial carcinoma — Tumors of the small glands in the airway walls. The same tumors occur in the salivary glands. Most arise in a large airway, and most grow slowly.

Three further answers describe the limits of what could be determined. “Carcinoma, type cannot be determined” and “non-small cell carcinoma, subtype cannot be determined” are used when the tissue does not allow a firm classification. The second is not considered acceptable on a resection specimen, where the whole tumor is available for examination. “No viable tumor present” means no living cancer cells remained, which is seen after successful treatment before surgery. Some reports add a histologic type comment, which is free text the pathologist uses to explain an unusual feature.

Growth patterns in adenocarcinoma

This item applies only to non-mucinous lung adenocarcinomas. Reports on every other type mark it “not applicable.” Most lung adenocarcinomas contain a mixture of growth patterns rather than a single one. The pathologist estimates how much of the tumor each pattern accounts for, in 5-percent steps, adding up to 100.

Lepidic — Tumor cells creeping along intact air sac walls. The most favorable pattern.
Acinar — Rounded glands. An intermediate pattern.
Papillary — Finger-like fronds with supporting cores. An intermediate pattern.
Solid — Sheets of cells with no gland formation. A high-grade pattern.
Micropapillary — Small tufts of cells without supporting cores. A high-grade pattern.
Complex glands — Glands fused together, or single cells infiltrating scar-like tissue, including a sieve-like cribriform arrangement. A high-grade pattern.

These percentages are not a curiosity. The pattern that makes up the largest share, combined with how much high-grade pattern is present, determines the histologic grade described in the next section.

Histologic grade

Histologic grade describes how closely lung cancer cells and the structures they form resemble normal lung. For non-mucinous adenocarcinoma, grade comes from a system published by the International Association for the Study of Lung Cancer. It combines two things: the growth pattern that makes up the largest share of the tumor, and the amount of high-grade pattern present anywhere in it. This combination predicts outcome better than the predominant pattern alone.

G1, well differentiated — Lepidic-predominant, with less than 20 percent high-grade pattern. Also used for typical carcinoid tumors.
G2, moderately differentiated — Acinar-predominant or papillary-predominant, with less than 20 percent high-grade pattern. Also used for atypical carcinoid tumors.
G3, poorly differentiated — Any adenocarcinoma with 20 percent or more of solid, micropapillary, cribriform, or complex glandular pattern, regardless of what the predominant pattern is.
G4, undifferentiated — Used for small cell carcinoma and large cell carcinoma.
GX, cannot be assessed — There was not enough tumor left to grade, which happens most often after treatment given before surgery.
Not applicable — No grading system exists for this tumor.

The 20 percent rule is the key part to understand. A lung adenocarcinoma that is mostly made of favorable-looking glands is still graded G3 if one-fifth of it shows a high-grade pattern, because that component drives behavior. This is why a report can describe a tumor as acinar-predominant and grade it poorly differentiated at the same time.

No accepted grading system currently exists for invasive mucinous adenocarcinoma or squamous cell carcinoma of the lung. Reports on those tumors either leave grade blank or use a general four-tier scale: well differentiated, moderately differentiated, poorly differentiated, and undifferentiated.

Spread through air spaces (STAS)

Spread through air spaces is usually shortened to STAS. It means that single lung cancer cells, or small clusters of them, were seen floating in the air spaces beyond the edge of the main tumor. The report states: not identified, present, cannot be determined, or not applicable.

STAS is associated with a higher chance that the cancer will come back. The association is strongest after a limited operation, such as a wedge resection or segmentectomy, where less surrounding lung is removed. Where STAS is found, the surgical team may discuss removing more tissue or arranging closer follow-up.

STAS is not added to the tumor measurement, so it does not change the size on your report. Its presence rules out two diagnoses: adenocarcinoma in situ and minimally invasive adenocarcinoma, because both require STAS to be absent.

Visceral pleural invasion

The pleura is the smooth membrane covering the lung surface. Visceral pleural invasion means the lung cancer has reached or passed through the elastic layer within that membrane. The report states not identified, present, or cannot be determined.

This item changes the stage. A tumor 3 centimeters or smaller that would otherwise be pT1 becomes pT2a once visceral pleural invasion is present. Few single findings in the report have such a large effect.

The boundary can be hard to judge on the routine stain, so pathologists sometimes use an elastic stain, which colors the elastic fibers and makes the layers easier to see. Two levels are recognized, and your report may name them. PL1 means the tumor has passed the outer elastic layer but has not reached the surface. PL2 means it reaches the surface. Both count as invasion and both raise the stage in the same way. PL0 means the tumor has not crossed the elastic layer and is reported as not identified.

Direct invasion of other structures

This item records whether the lung cancer has grown directly into a structure outside the lung. It is completed only when such a structure was removed with the specimen. Reports mark it “not applicable” when none was included, or “not identified” when the structures present were free of tumor. When invasion is present, the report names each structure involved.

Which structure is involved matters more than how many. The structures fall into three groups, and each group carries its own stage.

Structures that make the stage pT2a — An adjacent lobe of the lung. The main bronchus, up to but not including the carina. The soft tissue at the root of the lung. Collapsed lung or inflammation behind a blockage, extending toward the center of the chest.
Structures that make the stage pT3 — The parietal pleura, which is the lining of the chest wall. The chest wall itself, including its fat, muscle, and ribs. The parietal pericardium, which is the outer sac around the heart. The phrenic nerve. The azygos vein. The thoracic nerve roots or the stellate ganglion at the top of the chest.
Structures that make the stage pT4 — The mediastinum, which is the central compartment of the chest. The thymus, trachea, or carina. The recurrent laryngeal nerve or the vagus nerve. The esophagus. The diaphragm. The heart, or the visceral pericardium covering it. The great vessels, including the aorta and the vena cava. The supra-aortic arteries, brachiocephalic vein, or subclavian vessels. The vertebral body, lamina, spinal canal, cervical nerve roots, or brachial plexus.

A piece of tissue attached to a lung specimen may not be identifiable once it is out of the body. To assess these findings, the pathologist may need to read the operating note or speak with the surgeon.

Treatment effect after therapy given before surgery

Some patients with lung cancer receive chemotherapy, immunotherapy, targeted therapy, radiation, or a combination before surgery. This is called neoadjuvant or presurgical therapy, and it has become far more common as immunotherapy has moved into the treatment of operable lung cancer. When it has been given, the pathologist describes how much living cancer is left.

No known presurgical therapy — No treatment was given beforehand. This is what most reports say.
Not identified — Treatment was given, but the tissue shows no sign of having responded.
Present — A response is visible, and the report gives the percentage of the tumor bed that is still living cancer.

Your report may also give two further percentages: the share of the tumor bed that is dead tissue, and the share that is scarring and inflammation. The three figures add up to 100. The inflammation may also be rated as mild, moderate, or severe. The pathologist arrives at these figures by examining the whole area where the tumor was, which is why a treated specimen takes longer to report.

The number to look for is the percentage of living cancer remaining. When 10 percent or less remains, the response is called a major pathologic response. It is associated with substantially better long-term outcomes. When no living cancer remains anywhere, including in the lymph nodes, this is a complete pathologic response, and the stage is recorded as ypT0.

Reports on patients treated before surgery use the letter “y” before the stage, written as ypT and ypN. It shows that the stage describes the cancer after treatment rather than before it.

Lymphatic and vascular invasion

This item records whether lung cancer cells were seen inside vessels in the tissue around the tumor. Vessels are one route by which cancer reaches lymph nodes and other organs, so finding cells inside one indicates they have gained access to that route. It does not mean the cancer has spread. The pathologist selects every category that applies.

Not identified — No tumor cells were seen inside any vessel.
Lymphatic invasion present — Tumor cells are inside thin-walled lymphatic channels. This finding is most consistently associated with a poorer outcome.
Arterial invasion present — Tumor cells are inside an artery.
Venous invasion present — Tumor cells are inside a vein.
Cannot be determined — The finding could not be assessed, and the report explains why.

Lymphovascular invasion does not change the tumor stage, the nodal stage, or the overall stage group in lung cancer. It is used alongside other findings when discussing adjuvant treatment. Its presence does rule out the diagnoses of adenocarcinoma in situ and minimally invasive adenocarcinoma. Some reports add a tumor comment at the end of this section, which is free text covering anything the standard items do not capture.

Surgical margins

A margin is a surface that the surgeon cut or dissected in order to remove the specimen. The pathologist inks these surfaces, examines them under the microscope, and reports whether lung cancer reaches any of them and how close it comes. Which margins exist depends on the operation.

Bronchial margin — The cut end of the airway. Present in a lobectomy or pneumonectomy.
Vascular margin — The cut ends of the artery and vein serving the removed tissue.
Parenchymal margin — The cut or stapled edge of the lung tissue itself. This is the main margin in a wedge resection or segmentectomy.
Chest wall margin and other attached tissue margins — Present when a structure outside the lung was removed with the specimen.

The report first states whether all margins are negative for invasive tumor. When they are, it names the closest margin and gives the distance in centimeters. The distance may be an exact figure or stated as greater than, at least, or less than a number. When a margin is involved, the report names which. For the bronchial margin, it may add how the tumor reaches it. The three possibilities are the airway lining itself, lymphatic channels beneath that lining, and the soft tissue around the outside of the airway.

Margins are reported separately for non-invasive tumor. Three findings are covered. The first two are carcinoma in situ at the bronchial margin and at the lung tissue margin. The third is a lepidic component of an invasive adenocarcinoma reaching the lung tissue margin. All three are managed differently from invasive cancer at a margin.

The pleura covering the lung surface is not a surgical margin, because the surgeon did not cut through it. Tumor reaching that surface is recorded as visceral pleural invasion instead, and it affects the tumor stage. Some reports add a margin comment explaining an unusual finding.

Lymph nodes

Lymph nodes are small immune organs found throughout the body. Lung cancer reaches these nodes in a fairly predictable order. It arrives first at the nodes closest to the airway serving the tumor. From there it reaches the nodes at the root of the lung, and then the nodes in the center of the chest. Whether cancer is found in them, and how far from the tumor those nodes sit, is the strongest single factor in staging lung cancer.

Lung cancer lymph nodes are identified by numbered stations rather than by name alone. Each is labeled R for right or L for left, or given a plain number when it lies in the center of the chest. Your report lists which stations were examined and which contained cancer.

The numbering runs from the center of the chest outward, so a lower number generally means the cancer has traveled further. Working down from the top:

Stations 1 to 4 — Station 1 sits at the base of the neck. Stations 2 and 4 lie alongside the windpipe, and station 3 in front of it and behind it.
Stations 5 to 9 — Stations 5 and 6 sit near the aorta on the left. Station 7 lies beneath the point where the windpipe divides. Stations 8 and 9 lie lower in the chest.
Stations 10 to 14 — Station 10 sits at the root of the lung, and station 11 is between the lobes. Stations 12 to 14 lie within the lung itself.

Your report will also include:

Number of lymph nodes examined and number containing cancer — Given as an exact number. When nodes arrive in fragments and cannot be counted one by one, the report says “at least” a number instead. Nodes sampled by a scope before surgery are often fragmented in this way.
Lymph nodes from prior procedures — Whether nodes sampled at an earlier procedure, such as a mediastinoscopy or a scope-guided needle sampling, are included in this report or reported separately.
Size of the largest deposit — Measured in millimeters.
Extranodal extension — Cancer cells have broken through the outer capsule of a lymph node into the surrounding tissue. It may be associated with a poorer outcome. In lung cancer, it does not change the nodal stage or the overall stage group. A primary tumor growing directly into a neighboring node does not count as extranodal extension.

Distant metastasis

This item records whether lung cancer was confirmed under the microscope in a site outside the lung and its regional lymph nodes. It is completed only when tissue or fluid from that site was actually examined, and most reports mark it “not applicable” because distant spread is usually assessed by imaging.

Separate tumor nodules in a lobe on the opposite side — Cancer in the other lung.
Pleural or pericardial nodules — Deposits on the lining of the chest or the sac around the heart that are not directly connected to the main tumor.
Malignant pleural or pericardial effusion — Fluid around the lung or heart containing cancer cells. Some fluid tests negative for cancer time after time and is neither bloody nor high in protein. That fluid may be judged unrelated to the tumor and excluded from staging.
A single extrathoracic metastasis in one organ — One deposit outside the chest, including a single lymph node outside the regional group.
Multiple extrathoracic metastases in a single organ, or in multiple organs — Reported separately, because the two carry different stages.
Cannot be determined — The finding could not be established.

Pathologic stage (pTNM)

Pathologic stage summarizes how far the lung cancer had spread at the time of surgery. It is described using the TNM system from the American Joint Committee on Cancer (AJCC). Lung cancer now uses Version 9, which took effect for reporting in 2026. Version 9 keeps the tumor categories unchanged from the previous edition. It divides the nodal and metastasis categories more finely, so a stage assigned under the older system may not read exactly the same way.

T describes the size and extent of the tumor, N describes the lymph nodes, and M describes spread to distant organs. The letter “p” in front means the category was determined by examining tissue under the microscope.

Two prefixes may appear. A “y” means the stage was assigned after treatment given before surgery and describes what was present at the time of the operation. An “r” means the tumor is a recurrence, staged after a period during which no disease was detectable.

The pathologic stage on your report is not the same thing as the overall stage group, written as stage I through IV, that your oncologist will discuss with you. The stage group combines the T, N, and M categories into a single number and the treating physician assigns it using all available information, not the pathologist. A report that reads pT2a does not mean stage II.

Tumor stage (pT)

The tumor stage for lung cancer is based on the size of the invasive part of the tumor and on what it has grown into. When both apply, use the higher category.

pT0 — No cancer remains in the specimen, seen after successful treatment before surgery.
pTis — Carcinoma in situ, meaning either squamous cell carcinoma in situ or adenocarcinoma in situ, the latter being a purely lepidic adenocarcinoma 3 centimeters or smaller.
pT1mi — Minimally invasive adenocarcinoma, 3 centimeters or smaller and mostly lepidic, with 5 millimeters or less of invasion.
pT1a — Invasive tumor 1 centimeter or smaller. Also used for an uncommon superficial tumor confined to the wall of a bronchus, whatever its length.
pT1b — Larger than 1 centimeter but not larger than 2 centimeters.
pT1c — Larger than 2 centimeters but not larger than 3 centimeters.
pT2a — Larger than 3 centimeters but not larger than 4 centimeters. It is also used for a tumor 4 centimeters or smaller with any one of four features. These are invasion of the visceral pleura, invasion of an adjacent lobe, involvement of the main bronchus, and collapsed lung or obstructive inflammation extending toward the center of the chest.
pT2b — Larger than 4 centimeters but not larger than 5 centimeters, with or without the additional features listed above.
pT3 — Larger than 5 centimeters but not larger than 7 centimeters. It is also used for any tumor 7 centimeters or smaller that invades the parietal pleura or chest wall, the pericardium, the phrenic nerve, or the azygos vein. Separate tumor nodules in the same lobe also make a tumor pT3.
pT4 — Larger than 7 centimeters. It also applies to a tumor of any size that invades the mediastinum, heart, great vessels, trachea, carina, esophagus, diaphragm, or vertebral body. Invasion of the nerves listed earlier in this article counts as well. Separate tumor nodules in a different lobe on the same side also make a tumor pT4.
pT not assigned — The category could not be determined from the material available.

The letter “m” in brackets is added when several tumors of the same type were present and were too numerous to report individually.

Nodal stage (pN)

The nodal stage is based on where the involved lymph nodes sit rather than on how many contain cancer. Version 9 introduced the split within pN2 because the number of involved mediastinal stations predicted outcome better than involvement alone.

pN0 — No cancer in the lymph nodes examined.
pN1 — Cancer in nodes alongside the airway, at the root of the lung, or within the lung, all on the same side as the tumor. Nodes reached by the tumor growing directly into them count here.
pN2a — Cancer in a single mediastinal station on the same side, or in the station beneath the point where the windpipe divides.
pN2b — Cancer in more than one mediastinal station on the same side, with or without the station beneath the windpipe.
pN3 — Cancer in nodes on the opposite side of the chest, or in nodes at the base of the neck on either side.
pN not assigned — No nodes were submitted or found, or the category could not be determined.

Two labels may follow the nodal stage. “(sn)” means a sentinel node procedure was performed, and “(f)” means the node was sampled by a needle rather than removed whole.

Metastasis stage (pM)

The metastasis category is completed only when spread to a distant site was confirmed by examining tissue or fluid. Otherwise, the report marks it as not applicable.

pM1a — Deposits in the pleura or pericardium, malignant fluid around the lung or heart, or separate tumor nodules in a lobe on the opposite side. All of these remain within the chest.
pM1b — A single deposit outside the chest in one organ system, including a single lymph node outside the regional group.
pM1c1 — Several deposits outside the chest within a single organ system. The skeleton counts as one organ system, so several bone deposits fall here.
pM1c2 — Several deposits outside the chest in more than one organ system.

Other findings in the lung

When lung tissue is removed for cancer, the pathologist examines the surrounding lung as well and records any additional findings. None of these are cancer, and none change the stage. They are recorded because some mark increased risk in the remaining lung and others explain symptoms.

None identified — The surrounding lung was normal.
Atypical adenomatous hyperplasia — A small collection of mildly abnormal cells lining the air sacs, understood as the earliest step toward adenocarcinoma. It is not counted in staging and is not treated, but it may prompt closer attention to other small nodules on imaging.
Tumorlets — Tiny collections of neuroendocrine cells measuring less than 5 millimeters. Anything larger is called a carcinoid tumor.
Squamous dysplasia — Abnormal flat cells in the lining of an airway that fall short of carcinoma in situ. It is a marker of injury, usually from smoking.
Diffuse neuroendocrine hyperplasia — An increase in neuroendocrine cells throughout the airways. When it causes symptoms, it is known as DIPNECH and is followed over time.
Biopsy site changes — Scarring and inflammation at the spot where an earlier biopsy was taken.
Granulomatous inflammation — Tight clusters of immune cells, which the report describes as necrotizing or non-necrotizing. Causes include past infection and sarcoidosis, and this finding sometimes explains a second nodule seen on the scan.
Post-obstructive changes — Inflammation and trapped secretions in the lung beyond an airway the tumor was blocking.
Fibrosis — Scarring of the lung. The report describes the pattern, as some patterns represent an underlying lung disease that affects how much lung function can be spared.
Emphysema — Enlarged, damaged air sacs, usually from smoking. Its extent affects breathing capacity after surgery.
Other — Any additional finding, which the report describes.

Biomarker and molecular testing

Biomarker testing looks for specific changes in the genes and proteins of a lung cancer that determine which drugs are likely to work. These results are not part of the checklist described in this article. The resection checklist carries a single line, usually headed “special studies,” that points to a separate CAP biomarker template. That template is reported on its own, often days or weeks later, and sometimes by a different laboratory. Your report may say that testing is pending.

For non-small cell lung cancer, the panel usually covers EGFR, ALK, ROS1, RET, KRAS, BRAF, HER2 (ERBB2), MET, NTRK, and NRG1. It also covers PD-L1 and, in some laboratories, mismatch repair and tumor mutational burden. Testing is offered more selectively in squamous cell carcinoma, where these changes are uncommon. It is not currently used to guide treatment in small cell carcinoma or in carcinoid tumors.

Our guide to non-small cell lung cancer biomarker test results explains each of these tests, every result you might see, and what it means for treatment. You can also read about the individual tests in the Biomarkers and Genetic Testing section of this website.

What is the prognosis?

Prognosis is the expected course of a disease. Figures published for lung cancer as a whole include the many patients whose cancer had already spread when it was found. They therefore understate the outlook for someone whose cancer was removed by an operation.

Across all stages and types combined, roughly 28 out of every 100 people diagnosed with lung cancer are alive five years later. That figure has been rising steadily, as screening finds more cancers early and as targeted therapy and immunotherapy have changed what is possible in advanced disease. When a non-small cell lung cancer is still confined to the lung, roughly 65 to 70 out of every 100 people are alive at five years. When it has reached lymph nodes in the chest, that figure is closer to 38 out of 100.

Small cell carcinoma carries a less favorable outlook at every stage. Carcinoid tumors carry a considerably more favorable one, and most patients with a typical carcinoid removed by surgery are cured by the operation.

These figures describe large groups of people diagnosed years ago and cannot predict what will happen to any one person. Your own outlook depends on the combination of findings in your report, above all the following:

Lymph node status — The strongest single factor. Outcomes are best when no cancer is found in the nodes, and the risk rises as the involved nodes sit further from the tumor.
Tumor size and extent — Smaller invasive size and no growth into neighboring structures carry a lower risk of recurrence.
Histologic type — Carcinoid tumors carry the most favorable outlook, adenocarcinoma and squamous cell carcinoma an intermediate one, and small cell carcinoma and large cell neuroendocrine carcinoma the least favorable.
Histologic grade and growth pattern — Among adenocarcinomas, lepidic-predominant tumors recur least often and tumors with 20 percent or more solid, micropapillary, or complex glandular pattern recur most often.
Visceral pleural invasion — Associated with a higher risk of recurrence and raises the tumor stage.
Spread through air spaces — Associated with a higher risk of recurrence, particularly after a limited operation.
Lymphatic and vascular invasion — Associated with a higher risk of recurrence, though it does not change the stage.
Margin status — Cancer at a cut edge raises the risk that disease remains in the chest.
Response to treatment given before surgery — Where presurgical treatment was given, having 10 percent or less living cancer left is associated with substantially better long-term outcomes.
Stopping smoking — People who stop smoking after a lung cancer diagnosis have better outcomes than those who continue. They tolerate treatment better and face a lower risk of a second lung cancer. Your treatment team can arrange support.

What happens after this diagnosis?

The lung cancer pathology report is the document your treatment team uses to plan next steps. A group typically coordinates care, including a thoracic surgeon, a medical oncologist, a radiation oncologist, a respirologist, a pathologist, and a radiologist. They often review reports together at a tumor board meeting.

The findings on your report shape several decisions:

Chemotherapy after surgery — Considered when lymph nodes contain cancer. Also considered for a node-negative cancer larger than 4 centimeters, or one with other high-risk findings on the report.
Targeted therapy after surgery — Considered when the tumor carries an EGFR mutation or an ALK fusion. It is taken as a tablet for a period of years to reduce the chance that the cancer returns.
Immunotherapy after surgery — Considered based on stage and on the PD-L1 result, and given in addition to chemotherapy in many cases.
Radiation — Considered when a margin is involved, and sometimes when several mediastinal lymph nodes contain cancer.
Further surgery — A positive margin may lead to a discussion about removing more tissue, though this depends on how much lung function can be spared.
Treatment of remaining nodules — If other small nodules remain, the plan may be to monitor them. Many multifocal ground-glass nodules grow very slowly.
Follow-up — CT scans at intervals for several years, along with attention to breathing capacity and to smoking cessation where relevant.

If any part of your report is unclear, your treating physician can request the full report from the laboratory and go through it with you. You can also arrange a second opinion on the pathology if you would like one.

Questions to ask your doctor

What type of lung cancer do I have, and what does that type mean for my treatment?
What was the invasive tumor size on my report, and does it differ from the total tumor size?
What was the histologic grade, and what were the growth patterns and their percentages?
Does my report say that spread through air spaces was present, and what does that mean for me?
Was visceral pleural invasion identified, and did it change my tumor stage?
Which lymph node stations were examined, and which contained cancer?
Were all my margins negative, and how close did the tumor come to the closest one?
Does my report mention lymphatic, arterial, or venous invasion?
Has biomarker testing been ordered, and when will those results be available?
What is my overall stage group, and how does it relate to the pT and pN categories on my report?
If I had treatment before surgery, what percentage of living cancer was left?
Does anything on my report make targeted therapy or immunotherapy after surgery an option for me?
Do I need chemotherapy or radiation after this operation?
What is the follow-up plan, and what symptoms should prompt me to call?