Invasive Breast Cancer: Understanding Your Pathology Report After Surgery

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Invasive breast cancer is a cancer that starts in the ducts or milk-producing glands of the breast and grows into the surrounding breast tissue. “Invasive” means the tumor cells have broken through the thin layer of tissue that normally keeps them inside the ducts and glands. This is what pathologists mean by invasion. Once it happens, the cancer can reach nearby lymph nodes and, less often, spread to other parts of the body, which is called metastasis.

This article explains the pathology report created after surgery to remove an invasive breast cancer, either a lumpectomy (also called an excision or partial mastectomy) or a mastectomy. It covers every item your pathologist is required to report, in roughly the order you will find them, and it applies to all types of invasive breast cancer. Reading it will help you understand what each term means and why it matters for your care.

Why your pathology report looks like a checklist

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

One checklist covers all types of invasive breast cancer, so your report may list items that do not apply to your situation. 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.

How is the diagnosis made?

The diagnosis of invasive breast cancer is made when a tissue sample is examined under a microscope by a pathologist. In almost all cases, the first sample is a core needle biopsy taken through the skin with a hollow needle, usually guided by ultrasound or mammography. Surgery follows the biopsy, and the report described in this article comes from that surgical specimen.

Under the microscope, the pathologist looks for tumor cells that have spread out of the ducts and glands into the surrounding supporting tissue of the breast. Normal ducts and glands are surrounded by a continuous layer of cells called myoepithelial cells. In invasive cancer, that layer is absent around the tumor cells. When the distinction is difficult, the pathologist may perform immunohistochemistry, a test that uses colored stains to show specific proteins in tissue. Stains for myoepithelial proteins such as p63, calponin, and smooth muscle myosin heavy chain help confirm that invasion is present, because these cells are lost around invasive tumors. A stain for a protein called E-cadherin is often used to separate the two most common types of invasive breast cancer: it is present in ductal-type tumors and absent in most lobular tumors.

After invasive breast cancer is confirmed, imaging tests are performed to assess how far the disease has spread. These may include mammography and ultrasound of both breasts and the underarm area, and in some situations MRI, CT, bone scan, or PET scan. The pathology report describes what was found in the tissue that was removed; imaging describes the rest of the body.

The type of surgery and the side of the body

The first items on an invasive breast cancer pathology report describe the specimen, meaning the tissue that was sent to the laboratory, and which breast it came from.

Excision — Removal of the tumor along with a rim of surrounding breast tissue, leaving the rest of the breast in place. This may also be called a lumpectomy, a partial mastectomy, a segmental resection, or a quadrantectomy.
Total mastectomy — Removal of all of the breast tissue. This includes skin-sparing mastectomy (the nipple and a narrow rim of skin are removed, and most of the skin is kept for reconstruction) and nipple-sparing mastectomy (the skin and nipple are both kept).
Specimen laterality — Whether the tissue came from the right or the left breast. If both breasts contained cancer, each one is examined and reported separately, because each cancer is staged on its own.

The report may also note that lymph nodes from the underarm were removed with the breast tissue or submitted as a separate specimen.

Tumor focality: one tumor or more than one

Focality describes how many separate areas of invasive breast cancer were found in the breast. It is reported for every case.

Unifocal — A single area of invasive cancer.
Multifocal — More than one separate area of invasive cancer in the same breast. Areas at least 5 millimeters apart are generally counted as separate.

When more than one area is found, the pathologist also describes whether the areas look the same or different. Areas with similar size, grade, type, and biomarker results are usually branches of one cancer, and the report describes them together. Areas that differ from one another are treated as separate cancers, and the report may describe each one in its own section with a label such as “Lesion 1” and “Lesion 2.” Your report may also give the number of separate areas and where they were located.

Finding more than one area of cancer does not by itself mean the cancer is more advanced. Stage is based on the largest single area, not on the total of all areas added together. What multifocal disease does affect is surgical planning, because more than one area is harder to remove completely with a lumpectomy.

Types of invasive breast cancer (histologic type)

Histologic type describes what the invasive breast cancer looks like under the microscope and which normal breast structure it most resembles. Pathologists assign the type using the World Health Organization (WHO) classification of breast tumors. The type contributes to the overall picture of how the cancer is likely to behave, although hormone receptor status, HER2 status, grade, and stage carry more weight in treatment decisions than type alone.

Invasive carcinoma of no special type

Invasive carcinoma of no special type is the most common type of invasive breast cancer, accounting for roughly 70 to 80 out of every 100 cases. It is also called invasive ductal carcinoma, and many reports use both names. “No special type” does not mean the cancer is unusual or unclassifiable. It means the tumor does not show the specific pattern required for one of the named special types below, which is the situation for most breast cancers. Under the microscope, the tumor cells form irregular nests, cords, and glands that push through the supporting tissue of the breast, and the surrounding tissue often reacts by becoming dense and scar-like. This reaction is what makes many of these tumors feel firm and show up clearly on imaging.

Some tumors of no special type show a distinctive pattern that is described but does not change the type. Your report may mention neuroendocrine differentiation, a medullary pattern (sheets of tumor cells with many immune cells around them), or another rare pattern. These descriptions are recorded alongside the type rather than instead of it.

Invasive lobular carcinoma

Invasive lobular carcinoma is the second most common type, making up about 10 to 15 out of every 100 invasive breast cancers. It starts in the lobules, the small glands that produce milk. Its cells are small and uniform, and they characteristically spread through the breast in single files rather than forming a solid lump. Because of this growth pattern, lobular carcinoma can be harder to feel on examination and harder to measure on mammography, and it is more often found to be larger at surgery than imaging suggested. It is also more often multifocal and more often involves both breasts. Nearly all lobular carcinomas are hormone receptor positive.

Your report may describe the tumor as classic lobular carcinoma or as a variant pattern such as pleomorphic or histiocytoid. Pleomorphic lobular carcinoma has larger, more irregular nuclei and behaves more like a higher-grade cancer.

Mixed types

Some invasive breast cancers show more than one pattern. When a tumor combines ductal and lobular features, or combines a special type with no special type, the report describes it as a mixed type and gives the approximate percentage of each component. A tumor with both ductal and lobular features may also be called invasive mammary carcinoma. Treatment decisions generally follow the higher-risk component and the biomarker results.

Special types

Special types are diagnosed when at least 90 percent of the tumor shows a single distinctive pattern. Together they make up a small share of invasive breast cancers, and each of the following accounts for only about one or two out of every 100 cases or fewer.

Mucinous carcinoma — Tumor cells float in pools of mucus. Usually hormone receptor positive and low grade, with favorable outcomes.
Tubular carcinoma — Tumor cells form small, well-shaped tubes. Almost always low grade and hormone receptor positive, with very favorable outcomes.
Invasive cribriform carcinoma — Tumor cells form sheets punched through with round spaces, like a sieve. Closely related to tubular carcinoma and similarly favorable.
Invasive micropapillary carcinoma — Tumor cells form small clusters that sit in empty-looking spaces. Frequently associated with spread to lymph nodes.
Invasive apocrine carcinoma — Tumor cells have abundant pink cytoplasm and prominent nucleoli, resembling the cells of sweat glands. Often hormone receptor negative but positive for a different hormone receptor called the androgen receptor. When only part of the tumor shows these features, the report may instead say invasive ductal carcinoma with apocrine features.
Metaplastic carcinoma — The tumor cells change into a different cell type, such as spindle-shaped cells, squamous cells, or cells that form cartilage or bone. Most are triple negative. Two subtypes, low-grade adenosquamous carcinoma and fibromatosis-like metaplastic carcinoma, behave far more favorably than the others, which is why the report names the subtype.
Invasive solid papillary carcinoma — Tumor cells form rounded nodules supported by delicate blood vessels. Usually seen in older patients and usually hormone receptor positive. It is closely related to encapsulated papillary carcinoma, which grows within a cyst-like space and does not invade.
Adenoid cystic carcinoma — A rare tumor made of two cell types forming cylinders and sieve-like spaces. The same tumor occurs in the salivary glands, where it behaves very differently. Usually triple negative, but unlike most triple negative cancers it rarely spreads and has an excellent outlook.
Secretory carcinoma — A rare tumor whose cells produce abundant secretions, caused by a specific gene fusion. Slow growing, and the only type more common in children and young adults than in older adults.

If your tumor does not fit any listed category, the report will say “other histologic type” and describe what was seen.

Histologic grade (Nottingham score)

Histologic grade describes how different the invasive breast cancer cells look from normal breast cells and how quickly they are dividing. All invasive breast cancers are graded using the Nottingham histologic score, also called the Elston-Ellis modification of the Scarff-Bloom-Richardson system. The pathologist scores three features from 1 to 3 and adds them together.

Tubule formation — How much of the tumor is forming normal-looking gland structures. A score of 1 means more than 75 percent of the tumor forms glands, 2 means 10 to 75 percent, and 3 means less than 10 percent.
Nuclear pleomorphism — How much the nuclei, the control centers of the cells, vary in size and shape compared with normal breast cells. A score of 1 means they look nearly normal, and a score of 3 means they are large and highly irregular.
Mitotic rate — How many cells are actively dividing in a measured area of tumor. Dividing cells are called mitotic figures, and more of them means faster growth.

The three scores are added to give a total between 3 and 9, which becomes the overall grade:

Grade 1 (low grade, total score 3 to 5) — The tumor closely resembles normal breast tissue and is dividing slowly. These cancers tend to grow slowly and are less likely to spread.
Grade 2 (intermediate grade, total score 6 or 7) — The tumor falls between grades 1 and 3.
Grade 3 (high grade, total score 8 or 9) — The tumor looks very different from normal breast tissue and is dividing rapidly. These cancers tend to grow faster and are more likely to spread, and they are also more likely to respond well to chemotherapy.

Grade is one of the strongest predictors of outcome in invasive breast cancer, and it influences whether chemotherapy is considered and how genomic test results are interpreted. If the only invasive cancer found is a very small area measuring 1 millimeter or less, the report will state that grading was not performed, because there is not enough tumor to score reliably.

Tumor size

Tumor size is the largest measurement of the invasive breast cancer, given in millimeters. It is one of the two main factors that determine the stage of the cancer, along with the lymph nodes. The pathologist arrives at the size by combining what was seen with the naked eye, what was measured under the microscope, and what was reported on imaging.

Several rules affect how the number on your report was reached, and they explain why it may differ from the size you were told before surgery:

Only the invasive cancer is measured. — Any surrounding ductal carcinoma in situ is not included, even when it extends well beyond the invasive tumor.
Separate areas are not added together. — When there is more than one area of invasive cancer, the largest single area is used.
The needle biopsy is taken into account. — If a core needle biopsy removed part of the tumor and showed a larger area of invasion than the surgery did, the larger measurement is used. The two are never added together.
Microinvasion — An area of invasion measuring 1 millimeter or less. Reports use this term when the disease is almost entirely in situ with only a tiny focus of invasion.

Ductal carcinoma in situ (DCIS)

Ductal carcinoma in situ, usually shortened to DCIS, is a noninvasive cancer in which abnormal cells fill the ducts of the breast but have not broken through into the surrounding tissue. DCIS is found alongside invasive breast cancer in most cases, and the report describes it separately because it is measured, graded, and margin-assessed on its own. DCIS does not add to the size of the invasive tumor and does not change the stage.

Your report may include some or all of the following details about DCIS:

Extent — Whether the DCIS is mixed in with the invasive tumor, extends beyond it, or sits separately in the breast. It may be given as a percentage of the whole tumor or as a measurement in millimeters. Extensive DCIS matters mainly because it affects how much tissue needs to be removed to clear the margins.
Architectural pattern — The shape the cells make inside the duct: comedo, cribriform, micropapillary, papillary, solid, or others. Two patterns are named separately because they are managed differently: solid papillary carcinoma in situ and encapsulated papillary carcinoma. Pattern is recorded for completeness and has less effect on outcome than nuclear grade and necrosis.
Nuclear grade — Low (grade I), intermediate (grade II), or high (grade III), based on how abnormal the nuclei look.
Necrosis — Areas of dead tumor cells inside the ducts. Central or comedo necrosis fills the middle of the duct and is often what produces the calcium deposits seen on a mammogram. Focal necrosis means only small areas were found.

Other findings in the surrounding breast tissue

When breast tissue is removed for invasive breast cancer, the pathologist examines the surrounding tissue as well and reports any additional abnormal findings. None of these are cancer, and none change the stage of the invasive cancer. They matter because they are markers of increased risk in both breasts over the following years, which can influence the follow-up plan.

Lobular carcinoma in situ (LCIS) — Abnormal cells filling and expanding the lobules without invading. Classic LCIS is a risk marker rather than a cancer that is expected to grow into one. Pleomorphic and florid variants are less common, are managed more like DCIS, and are named specifically when present.
Atypical ductal hyperplasia (ADH) — An overgrowth of abnormal cells in a duct that falls short of the amount needed to call it DCIS.
Atypical lobular hyperplasia (ALH) — The same process as LCIS but involving fewer cells and less of the lobule.
Flat epithelial atypia (FEA) — A single layer of mildly abnormal cells lining a duct or lobule, often found near calcium deposits.

Tumor extent: nipple, skin, and muscle

This part of the report describes whether the invasive breast cancer has reached structures at the front or back of the breast. It is completed only when the nipple, skin, or muscle was included in the surgery, which is usually the case for a mastectomy and often not the case for a lumpectomy. If the report says “not applicable,” those structures were either not removed or were normal and did not need to be described.

Nipple — The report states whether the nipple was present and, if so, whether it was involved. Involvement can take the form of Paget disease (cancer cells growing within the skin of the nipple), DCIS in the large ducts beneath the nipple, or invasive cancer growing into the nipple. Nipple involvement affects surgical planning and the risk of local recurrence, but it does not change the stage.
Skin — The report states whether cancer has grown into the skin and, if so, whether the surface of the skin has broken down. Growth into the deeper layers of skin without an open sore does not change the stage. A visible sore (ulceration) or visible separate cancer nodules in the skin do change the stage to pT4b.
Skeletal muscle — The muscle at the back of a mastectomy specimen is usually the pectoralis muscle. Growth into this muscle is reported and can influence decisions about radiation, but it does not by itself change the stage. Only growth deeper than the pectoralis muscle, into the chest wall, is classified as pT4a, and this is usually determined by imaging and by what the surgeon finds.

Lymphovascular invasion

Lymphovascular invasion means that cancer cells were seen inside small blood vessels or lymphatic channels in the breast tissue outside the main tumor. These vessels are one of the routes by which invasive breast cancer reaches lymph nodes and other organs, so their involvement indicates that cells have gained access to that route. It does not mean the cancer has spread, and many patients with lymphovascular invasion have no cancer in their lymph nodes.

The report describes lymphovascular invasion as not identified, present and focal (limited to one or two vessels in a single tissue block), or present and extensive (more vessels, or vessels in more than one block). Lymphovascular invasion is associated with a higher chance of recurrence and may be taken into account when discussing radiation and systemic therapy.

If skin was removed with the specimen, the report separately states whether cancer cells were seen in the lymphatic channels of the skin. This finding, called dermal lymphovascular invasion, matters because it is the tissue change underlying inflammatory breast cancer. On its own it does not make a cancer inflammatory. That diagnosis requires the clinical findings of redness and swelling over at least a third of the breast.

Microcalcifications

Microcalcifications are tiny deposits of calcium in breast tissue. They are not cancer, and most are found in normal or benign tissue, but they show up clearly on a mammogram and are frequently the reason a breast abnormality is investigated in the first place. When calcifications were the target of the procedure, the pathologist confirms that they are present in the tissue removed and reports where they were found: in the invasive cancer, in DCIS, or in surrounding noncancerous tissue.

This item exists to confirm that the area the radiologist was concerned about was actually sampled and examined. It has no effect on stage or treatment.

Treatment effect after chemotherapy given before surgery

Some patients receive chemotherapy, HER2-targeted therapy, or hormone-blocking therapy before surgery. This is called neoadjuvant or presurgical therapy. When it has been given, the pathologist describes how much cancer is left and how much the treatment appears to have changed it. This item is one of the strongest predictors of long-term outcome in invasive breast cancer.

The report states whether there is no known presurgical therapy, no definite response, evidence of response, or no remaining invasive cancer in the breast. When treatment has worked well, the tumor often does not simply shrink into a smaller lump. Instead, scattered small areas of cancer remain in a larger scarred area called the tumor bed, and only the largest continuous area is used for staging. When no invasive cancer remains in either the breast or the lymph nodes, this is called a pathologic complete response, and it is associated with substantially better long-term outcomes.

Reports on patients treated before surgery use the letter “y” in front of the stage, written as ypT and ypN, to show that the stage reflects the cancer after treatment rather than before it. Many reports also include the residual cancer burden (RCB), a score that combines the size of the tumor bed, the proportion of it that still contains cancer, and the amount of cancer in the lymph nodes. It is reported as a class from RCB-0 to RCB-III.

RCB-0 — No remaining invasive cancer, the same as a pathologic complete response.
RCB-I — A minimal amount of cancer remaining.
RCB-II — A moderate amount of cancer remaining.
RCB-III — An extensive amount of cancer remaining.

Surgical margins

A margin is the cut edge of the tissue removed at surgery. Before examining the specimen, the pathologist coats these edges with ink so that they can be identified under the microscope, and then measures how close the invasive breast cancer and any DCIS come to the inked edge. Because invasive cancer and DCIS are managed differently, margins are reported separately for each.

Negative margin — No cancer cells at the inked edge. Your report may specify how close the closest cancer cells came, using categories such as within 1 millimeter, 1 to 2 millimeters, or more than 2 millimeters.
Positive (involved) margin — Cancer cells are present at the inked edge. When the specimen was marked for orientation, the report names which edge is involved, such as superior, inferior, medial, lateral, anterior, or deep.

For invasive breast cancer treated with lumpectomy followed by radiation, the widely used standard is “no ink on tumor,” meaning that a margin without cancer cells at the edge is considered adequate even when it is very thin. For DCIS treated the same way, a wider clearance of 2 millimeters is generally used. A positive margin raises the chance that cancer cells remain in the breast, and the surgical team may discuss removing more tissue. Distance to the deep margin at the chest wall and the front margin just under the skin is interpreted differently, because there is little or no breast tissue beyond those planes to remove.

If additional tissue was taken during the same operation or at a second operation, the final margin status takes those extra specimens into account, which is why the final statement on your report may differ from an earlier one.

Lymph nodes

Lymph nodes are small immune organs found throughout the body. Invasive breast cancer usually reaches the lymph nodes in the underarm (axilla) first, which is why these nodes are examined at surgery. Whether cancer is found in them is the single most important factor in staging invasive breast cancer.

Most patients have a sentinel lymph node biopsy, in which a dye or a radioactive tracer identifies the first few nodes that drain the breast, and only those are removed. If cancer is found in enough of them, or if nodes were known to be involved before surgery, a larger operation called an axillary dissection may be performed to remove more nodes.

Your report will include:

Total number of lymph nodes examined — All nodes found in the tissue submitted, sentinel and non-sentinel together.
Number of nodes containing cancer — Counted separately by the size of the largest deposit in each node.
Size of the largest deposit — Measured in millimeters, and used to place the deposits in one of the three categories below.
Extranodal extension — Cancer cells have broken through the outer capsule of a lymph node into the surrounding fat. When present, the report may give the size of the extension and the number of nodes involved. It is associated with a higher chance of recurrence and may be taken into account when radiation to the underarm is discussed.

Deposits of cancer in a lymph node are grouped by size, and the groups are treated very differently:

Isolated tumor cells — Single cells or clusters measuring 0.2 millimeters or less, or fewer than 200 cells. Nodes containing only isolated tumor cells are not counted as positive nodes, and the stage is recorded as pN0(i+).
Micrometastases — Deposits larger than 0.2 millimeters but not larger than 2 millimeters, or more than 200 cells. If these are the only deposits found, the stage is pN1mi.
Macrometastases — Deposits larger than 2 millimeters. These are the deposits that determine the nodal stage categories below.

Finding cancer in a small number of nodes does not automatically mean more surgery. Current practice allows many patients with one or two involved sentinel nodes who are having a lumpectomy with radiation to avoid a full axillary dissection, and your surgical team can explain how this applies to your situation.

Pathologic stage (pTNM)

Pathologic stage summarizes how far the invasive breast cancer had spread at the time of surgery. It is described using the TNM system from the American Joint Committee on Cancer (AJCC), 8th edition, where 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. M is almost always determined by imaging rather than by the pathologist, so most reports leave it blank or mark it not applicable.

The pathologic stage on your report is not the same thing as the overall stage group (stage I through IV) that your oncologist will discuss with you. For invasive breast cancer, that stage group also incorporates grade, estrogen receptor, progesterone receptor, and HER2 results, and it is assigned by the treating physician rather than by the pathologist.

Tumor stage (pT)

The tumor stage for invasive breast cancer is based on the size of the largest invasive tumor and, in a small number of cases, on growth into the chest wall or skin.

pT1mi — Tumor 1 millimeter or less (microinvasion).
pT1a — Tumor larger than 1 millimeter but not larger than 5 millimeters.
pT1b — Tumor larger than 5 millimeters but not larger than 10 millimeters.
pT1c — Tumor larger than 10 millimeters but not larger than 20 millimeters.
pT2 — Tumor larger than 20 millimeters but not larger than 50 millimeters.
pT3 — Tumor larger than 50 millimeters.
pT4a — Tumor of any size growing into the chest wall, beyond the pectoralis muscle.
pT4b — Tumor of any size with a visible open sore in the skin, visible separate cancer nodules in the skin of the same breast, or swelling of the skin.
pT4c — Both pT4a and pT4b are present.
pT4d — Inflammatory breast cancer, diagnosed when at least a third of the breast is red and swollen.

Two additional labels may appear. The letter “m” in brackets means more than one separate tumor was present. The letters “pTis” mean that only in situ cancer was found, which after presurgical treatment indicates that all of the invasive cancer is gone.

Nodal stage (pN)

The nodal stage is based on how many lymph nodes contain cancer and how large the deposits are.

pN0 — No cancer found in the lymph nodes examined.
pN0(i+) — Only isolated tumor cells found, measuring 0.2 millimeters or less.
pN1mi — Micrometastases only, larger than 0.2 millimeters but none larger than 2 millimeters.
pN1a — Cancer in 1 to 3 underarm lymph nodes, with at least one deposit larger than 2 millimeters.
pN1b — Cancer in the internal mammary sentinel nodes, which sit beside the breastbone.
pN1c — pN1a and pN1b together.
pN2a — Cancer in 4 to 9 underarm lymph nodes.
pN2b — Cancer in internal mammary nodes seen on imaging, with no cancer in the underarm nodes.
pN3a — Cancer in 10 or more underarm lymph nodes, or in the nodes beneath the collarbone.
pN3b — Cancer in both underarm and internal mammary nodes in specified combinations.
pN3c — Cancer in the lymph nodes above the collarbone on the same side.

The label “(sn)” after the nodal stage means the stage was based on a sentinel lymph node biopsy in which fewer than six nodes were removed.

Biomarker and molecular testing

Biomarker testing is part of the workup of every invasive breast cancer. These tests measure specific proteins and genes in the tumor and determine which treatments are likely to work. They are usually performed on the original needle biopsy, and the results are often repeated in the surgical report for completeness. If the results appear in the section of your report labeled “special studies” or “prior biomarker results,” they came from an earlier specimen, and the report will say which one.

Estrogen receptor and progesterone receptor

The estrogen receptor (ER) and progesterone receptor (PR) are proteins that allow breast cells to respond to the hormones estrogen and progesterone. When a breast cancer carries these receptors, its growth is driven in part by hormones, and blocking them slows the cancer. Both are tested by immunohistochemistry and reported as the percentage of tumor cells with staining in the nucleus.

ER positive — More than 10 percent of tumor cells show staining. About three quarters of invasive breast cancers fall here, and these patients are candidates for hormone-blocking therapy such as tamoxifen or an aromatase inhibitor.
ER low positive — Staining in 1 to 10 percent of cells. This result is reported as its own category because these cancers often behave more like ER negative cancers, and the benefit of hormone-blocking therapy is less certain.
ER negative — Fewer than 1 percent of cells show staining. Hormone-blocking therapy is not expected to help.
PR positive or negative — Reported the same way, with 1 percent as the threshold. PR adds prognostic information, but ER is the main determinant of hormone therapy eligibility.

HER2

HER2 is a protein on the surface of breast cells that signals them to grow. Some invasive breast cancers make far too much of it, usually because the tumor carries extra copies of the HER2 gene, and these cancers grow faster but respond to drugs that target HER2 directly. Testing begins with immunohistochemistry, which is scored from 0 to 3+. Equivocal results go on to in situ hybridization, which counts the actual copies of the gene.

Positive (score 3+, or 2+ with amplification on in situ hybridization) — The cancer is HER2 positive. This makes drugs such as trastuzumab, pertuzumab, and trastuzumab deruxtecan available, and these have changed the outlook for HER2 positive breast cancer dramatically.
Equivocal (score 2+) — The immunohistochemistry result is in between, and in situ hybridization decides. If the gene is not amplified, the cancer is treated as HER2 negative and falls into the HER2-low group below.
Score 1+ or 2+ without amplification (HER2-low) — Not HER2 positive in the traditional sense, but with enough HER2 present that trastuzumab deruxtecan can be considered for advanced disease.
Score 0 with faint staining in 10 percent or fewer cells (HER2-ultralow) — A category recently separated out on reports. Even this small amount of HER2 now identifies patients with hormone receptor positive advanced breast cancer who may benefit from trastuzumab deruxtecan.
Score 0 with no staining at all — No HER2 protein detected. HER2-directed treatment is not expected to help.

The reason your report distinguishes between complete absence of staining and faint staining is that this line now separates two groups with different treatment options, which was not the case a few years ago.

Ki-67

Ki-67 is a protein found only in cells that are actively dividing. It is measured by immunohistochemistry and reported as the percentage of tumor cells that show staining, so a higher number means a faster-growing invasive breast cancer. Ki-67 is used alongside grade, stage, and receptor status rather than on its own, and laboratories differ in how they measure it, so results are not always directly comparable between reports.

Genomic tests

Genomic tests measure the activity of a panel of genes in the tumor to estimate the risk that an invasive breast cancer will return and how much benefit chemotherapy would add. They are used mainly in hormone receptor positive, HER2 negative cancers, where the decision about chemotherapy is often finely balanced. The available tests include the 21-gene recurrence score (Oncotype DX), the 70-gene signature (MammaPrint), and the 50-gene assay (Prosigna). These tests are performed at specialized laboratories on the tissue already in storage, so the result usually arrives separately, days or weeks after the pathology report.

PD-L1

PD-L1 is a protein that some tumors use to switch off the immune cells that would otherwise attack them. Testing for it is limited to triple negative breast cancer, meaning cancers that are ER negative, PR negative, and HER2 negative. It is measured by immunohistochemistry and reported as a combined positive score (CPS). A score of 10 or higher indicates eligibility for the immunotherapy drug pembrolizumab in advanced or metastatic disease. In early-stage triple negative breast cancer treated before surgery, immunotherapy is used regardless of the PD-L1 result, so the test is not required in that setting.

PIK3CA, AKT1, PTEN, and ESR1

These genes control signals that tell breast cancer cells to grow, or in the case of ESR1, the estrogen receptor itself. Changes in them are usually tested by sequencing the tumor or, for ESR1, a blood sample, and testing is generally reserved for hormone receptor positive cancers that have spread or have stopped responding to hormone-blocking therapy. A change in PIK3CA, AKT1, or PTEN indicates eligibility for drugs such as alpelisib or capivasertib. A change in ESR1 explains resistance to some hormone therapies and indicates eligibility for elacestrant. These changes are usually acquired by the tumor during life and are not inherited.

BRCA1, BRCA2, and inherited risk

BRCA1 and BRCA2 are genes that repair damaged DNA. People who inherit a faulty copy have a substantially higher lifetime risk of breast and ovarian cancer, and their tumors respond to a class of drugs called PARP inhibitors. Testing for an inherited change requires a separate blood or saliva sample, not the tumor tissue, and is arranged through a genetics service. Guidelines now offer this testing to a wide group of patients with breast cancer, including anyone diagnosed at a young age, anyone with triple negative breast cancer, anyone with a significant family history, and any man with breast cancer.

You can read more about the tests described here in the Biomarkers and Genetic Testing section of this website.

What is the prognosis?

Prognosis is the expected course of a disease. For invasive breast cancer, the outlook is generally favorable, and it has improved steadily over the past three decades as screening has found cancers earlier and treatment has improved. Across all stages combined, roughly 90 out of every 100 women diagnosed with invasive breast cancer are alive five years later. When the cancer is confined to the breast, that figure is about 99 out of 100. When it has reached nearby lymph nodes, it is about 86 out of 100. When it has spread to distant organs, it is closer to 30 out of 100, although this number is rising as new treatments are introduced and it varies a great deal by subtype.

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 risk rises with the number of nodes involved.
Tumor size — Smaller invasive cancers carry a lower risk of recurrence.
Histologic grade — Grade 1 cancers recur less often than grade 3 cancers.
Receptor and HER2 status — Hormone receptor positive cancers can be treated with hormone-blocking therapy for years and generally carry a better long-term outlook. HER2 positive cancers, once among the hardest to treat, now respond well to HER2-targeted drugs. Triple negative cancers have fewer targeted options and a higher risk of early recurrence, although they often respond strongly to chemotherapy.
Lymphovascular invasion — Associated with a higher risk of recurrence.
Response to treatment given before surgery — Where presurgical treatment was given, having no remaining invasive cancer is associated with substantially better long-term outcomes, particularly in triple negative and HER2 positive disease.
Genomic test results — Where performed, these refine the estimate of recurrence risk beyond what the other features can provide.

What happens after this diagnosis?

The pathology report for an invasive breast cancer is the document your treatment team uses to plan what comes next. Care is coordinated by a group that typically includes a surgeon, a medical oncologist, a radiation oncologist, a pathologist, and a radiologist, who often review reports together at a tumor board meeting.

The findings on your report shape several decisions:

Further surgery — A positive margin may lead to a discussion about removing more tissue. Cancer found in the sentinel lymph nodes may lead to a discussion about removing more nodes, though this is needed less often than it once was.
Radiation — Almost always considered after a lumpectomy. After a mastectomy, it is considered when the tumor was large, when several lymph nodes were involved, or when margins were positive.
Hormone-blocking therapy — Considered when the cancer is estrogen receptor positive, usually taken for at least five years.
HER2-targeted therapy — Considered when the cancer is HER2 positive.
Chemotherapy — Considered based on stage, grade, receptor status, and, in hormone receptor positive cancers, the genomic test result.
Genetic assessment — Considered based on age at diagnosis, tumor subtype, and family history.
Follow-up — Regular examinations and imaging of the remaining breast tissue, and monitoring for side effects of long-term therapy.

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, and a second opinion on the pathology can be arranged if you would like one.

Questions to ask your doctor

What type of invasive breast cancer do I have, and what does that type mean for me?
What was the size of the invasive cancer, and what was the grade?
Was there more than one area of invasive cancer in my breast?
How many lymph nodes were removed, and how many contained cancer?
Was extranodal extension found in any of the lymph nodes?
Were my margins clear, and does anything about them mean more surgery?
Was lymphovascular invasion found in my tumor?
What are my estrogen receptor, progesterone receptor, and HER2 results, and what treatments do they make available to me?
Is my cancer HER2-low or HER2-ultralow, and does that matter for me now or later?
Will a genomic test such as Oncotype DX, MammaPrint, or Prosigna be ordered, and how will the result be used?
What is my overall stage, and how does it compare with the pathologic stage on my report?
If I had treatment before surgery, how much cancer was left, and what does that mean for my outlook?
Should I be referred for genetic testing based on my diagnosis and family history?
What is the follow-up plan, and what symptoms should prompt me to call?