Intramucosal Adenocarcinoma of the Esophagus: Understanding Your Pathology Report

by Catherine Forse MD FRCPC and Jason Wasserman MD PhD FRCPC
July 29, 2026

Intramucosal adenocarcinoma of the esophagus is an early form of cancer that starts in the gland-forming cells lining the esophagus, the muscular tube that carries food from the mouth to the stomach. The word adenocarcinoma means the cancer arose from glandular cells, the cells that normally make and release mucus. The word intramucosal means the cancer is still confined to the mucosa, the thin innermost lining of the esophagus, and has not grown into the deeper layers of the wall.

This distinction matters a great deal. Because the tumor has not reached the deeper layers where most of the blood vessels and lymphatic channels run, the chance that it has spread elsewhere in the body is very low. For most people, intramucosal adenocarcinoma can be removed completely through an endoscope, without an operation to remove part of the esophagus.

Your report may describe this diagnosis using any of several phrases: intramucosal adenocarcinoma, intramucosal carcinoma, adenocarcinoma with invasion limited to the mucosa, or adenocarcinoma, pT1a. These all describe the same finding. This article will help you understand the findings in your pathology report, what each term means, and why it matters for your care.

What causes intramucosal adenocarcinoma of the esophagus?

Almost all intramucosal adenocarcinomas of the esophagus develop in a person who already has Barrett esophagus. Barrett esophagus is a change in the lining of the lower esophagus in which the normal flat squamous cells are replaced by gland-forming cells that look like the cells normally found in the intestine. This change is called intestinal metaplasia.

Barrett esophagus develops after years of exposure to stomach acid and bile, usually because of gastroesophageal reflux disease (GERD), a condition in which stomach contents flow backward into the esophagus. Over time, the glandular cells in Barrett esophagus can accumulate genetic damage and begin to look abnormal under the microscope, a change called dysplasia. Dysplasia typically progresses in steps, from low-grade dysplasia to high-grade dysplasia, and finally to intramucosal adenocarcinoma, when the abnormal cells break out of the glands and begin to grow into the surrounding tissue of the mucosa.

Most people with Barrett esophagus never develop cancer. Factors that raise the risk include long-standing and poorly controlled reflux, a longer segment of Barrett esophagus, obesity (particularly weight carried around the abdomen), smoking, older age, male sex, and being of white European ancestry. A family history of Barrett esophagus or esophageal adenocarcinoma also increases risk. Intramucosal adenocarcinoma is not caused by anything you did or failed to do, and it is not contagious or inherited in a simple way.

What are the symptoms of intramucosal adenocarcinoma of the esophagus?

Intramucosal adenocarcinoma of the esophagus is small and confined to the inner lining, so it usually causes no symptoms of its own. Most cases are found during a routine surveillance endoscopy in a person already known to have Barrett esophagus, or unexpectedly during an endoscopy performed for reflux symptoms.

When symptoms are present, they usually come from the underlying reflux and Barrett esophagus rather than from the cancer itself. These may include heartburn, regurgitation of sour fluid, chest discomfort, or a sensation of food sticking. Difficulty swallowing (dysphagia) and unexplained weight loss are uncommon at this stage and, when present, raise the possibility of a deeper or larger tumor that needs further assessment.

How is the diagnosis made?

The diagnosis of intramucosal adenocarcinoma of the esophagus is made only after tissue from the esophagus is examined under a microscope by a pathologist. The tissue is obtained during an upper endoscopy, a procedure in which a thin flexible tube with a camera is passed through the mouth into the esophagus. Abnormal areas within the Barrett segment may be sampled with a small biopsy, or removed in one piece by endoscopic mucosal resection (EMR) or endoscopic submucosal dissection (ESD).

A small biopsy can show that cancer is present, but it often cannot show how deep the cancer goes, because the deeper layers of the esophageal wall are not included in the sample. For this reason, an endoscopic resection is usually performed after a biopsy diagnosis. The resection both removes the tumor and provides the full-thickness view of the mucosa that is needed to confirm the cancer has not reached the deeper layers.

Under the microscope, the pathologist looks for glands that are crowded, fused, or growing back-to-back, and for tumor cells that have escaped the glands and are growing directly into the surrounding tissue of the mucosa. The tumor cells show atypia, meaning enlarged, dark-staining nuclei (the part of the cell holding the genetic material), and they lose the orderly arrangement seen in normal glands. Critically, the pathologist confirms that this growth is limited to the mucosa and does not reach the submucosa, the layer beneath. Because this judgment can be difficult, the tissue is usually cut at multiple levels and examined carefully across the whole specimen, and many centers ask a second pathologist with expertise in gastrointestinal pathology to review the case before the diagnosis is finalized.

Immunohistochemistry, a test that uses antibodies to detect specific proteins inside cells, may be used to support the diagnosis. Tumor cells usually show cytokeratin 7 (CK7) and often CDX2, a pattern consistent with a cancer arising from the intestinal-type lining of Barrett esophagus. A stain for the p53 protein is sometimes added, because an abnormal p53 pattern supports a diagnosis of dysplasia or cancer rather than reactive change. These stains help confirm what the tumor is; they are different from the biomarker tests described later in this article, which are used to guide drug treatment for advanced disease.

Once the diagnosis is confirmed, imaging is usually performed to make sure no disease is present elsewhere. This typically includes a CT scan of the chest and abdomen, and sometimes endoscopic ultrasound or a PET scan. Imaging is far less accurate than the microscope for judging depth in very early tumors, so the pathology report remains the most reliable source of that information.

Histologic grade

Histologic grade describes how closely the cancer cells in an intramucosal adenocarcinoma of the esophagus resemble the normal gland-forming cells they came from. The pathologist assigns the grade by looking at how much of the tumor still forms recognizable glands. Grade is included in the report because it is one of the features used to estimate how likely the cancer is to have spread beyond the esophagus.

Well differentiated (G1) — More than 95% of the tumor forms recognizable glands. These tumors most closely resemble normal tissue and carry the lowest risk of spread. Your report may use the term well differentiated.
Moderately differentiated (G2) — Between 50% and 95% of the tumor forms glands. The remainder grows in sheets or cords of cells.
Poorly differentiated (G3) — Less than 50% of the tumor forms glands. These tumors show the greatest departure from normal tissue and carry a higher risk of spread to lymph nodes. Your report may use the term poorly differentiated.

Well differentiated and moderately differentiated tumors are often grouped together as low grade, and poorly differentiated tumors as high grade. Grade is one of the two findings, along with lymphovascular invasion, that most strongly influence whether removing the tumor through the endoscope is considered sufficient treatment. Grading a very small sample can be difficult, and the grade given on an initial biopsy is sometimes revised after the full resection specimen is examined.

Depth of invasion

Depth of invasion describes how far an intramucosal adenocarcinoma has grown into the wall of the esophagus, and it is the single most important finding on the report. The esophageal wall is built in layers. The innermost layer, the mucosa, is itself made of three thin sublayers: the surface epithelium, the lamina propria (a supportive layer of connective tissue), and the muscularis mucosae (a thin band of muscle at the base of the mucosa). Beneath the mucosa lies the submucosa, which carries the larger blood vessels and lymphatic channels, and beneath that the muscularis propria, the thick muscle layer that pushes food toward the stomach.

In intramucosal adenocarcinoma, the cancer has grown into the lamina propria or the muscularis mucosae but has not reached the submucosa. Because the mucosa contains very few lymphatic channels, cancer confined to this layer has few routes by which to travel to lymph nodes or to other organs. This is why intramucosal adenocarcinoma can usually be cured by removing the affected area of lining alone.

Some reports subdivide the depth further, using labels such as m1 (limited to the surface epithelium), m2 (into the lamina propria), or m3 (into the muscularis mucosae). In Barrett esophagus, the muscularis mucosae is often duplicated into two thin bands, so a report may also specify whether the tumor lies above, between, or below them. All of these findings still fall within the mucosa and are staged as pT1a.

Once a tumor crosses into the submucosa, it is staged as pT1b, and the risk of spread to lymph nodes rises sharply, from a few percent to roughly one in four. Confirming that a tumor is pT1a rather than pT1b is therefore the finding that most directly shapes what happens next.

Lymphovascular invasion

Lymphovascular invasion means that cancer cells from the intramucosal adenocarcinoma were seen inside a small blood vessel or lymphatic channel. It is reported as present or absent. Because these channels carry fluid and cells away from the esophagus, tumor cells inside them may be able to travel to lymph nodes or to distant organs.

Lymphovascular invasion is uncommon in tumors confined to the mucosa, but when it is found, it is the strongest single predictor that cancer cells have reached the lymph nodes. Its presence usually prompts the treatment team to consider whether treatment beyond endoscopic removal is needed. When the finding is difficult to judge, immunohistochemical stains that highlight the lining of blood vessels and lymphatic channels may be used to confirm it.

Perineural invasion

Perineural invasion means that cancer cells were seen surrounding or growing into a nerve. Like lymphovascular invasion, it is reported as present or absent in an intramucosal adenocarcinoma of the esophagus.

Nerves lie mostly in the deeper layers of the esophageal wall, so perineural invasion is rare in a tumor confined to the mucosa and is almost always reported as absent. If it is reported as present, the treatment team will look carefully at whether the tumor extends deeper than the mucosa.

Surgical margins

A margin is the cut edge of the tissue removed during an endoscopic resection or an operation. For an intramucosal adenocarcinoma of the esophagus, the pathologist inks these edges and examines them under the microscope to determine whether the tumor was completely removed. Two margins are examined on an endoscopic specimen:

Deep (vertical) margin — The deepest cut surface of the specimen, beneath the tumor. This is the more important of the two. A clear deep margin supports the conclusion that the tumor did not extend into the submucosa.
Lateral (mucosal or horizontal) margin — The side edges of the removed piece of lining. Cancer or dysplasia reaching a lateral margin means abnormal tissue may remain in the surrounding lining.

The results are reported as follows:

Negative margin — No cancer cells reach the inked edge. The report may also give the distance in millimeters between the tumor and the closest edge. A complete removal with all margins negative is sometimes described as an R0 resection.
Positive margin — Cancer cells extend to the inked edge, which means the tumor may remain in the esophagus. This is sometimes described as an R1 resection. A positive deep margin is more concerning than a positive lateral margin, because it raises the possibility that the tumor was cut across at its base and may reach deeper than the specimen shows.
Cannot be assessed — When a lesion is removed in several pieces rather than in one piece, the fragments cannot always be fitted back together, and the lateral margin may be impossible to evaluate. This is a limitation of the specimen rather than a finding about the tumor.

If a resection specimen also removes part of the esophagus itself, the report will describe proximal, distal, and radial (circumferential) margins instead.

Lymph nodes

Lymph nodes are small immune organs found throughout the body, including alongside the esophagus. Cancer cells can travel to them through lymphatic channels, and finding cancer in a lymph node is called a metastasis.

Most people with intramucosal adenocarcinoma of the esophagus will not see lymph nodes mentioned on their report at all. Endoscopic mucosal resection and endoscopic submucosal dissection remove only the inner lining and do not include lymph nodes, so there are none to examine. This is not an omission or an incomplete report. It reflects the fact that cancer confined to the mucosa spreads to lymph nodes in only about 2% to 4% of cases, which is why removing lymph nodes is not considered necessary for most patients.

If the esophagus is removed surgically, lymph nodes are taken at the same time, and the report will state how many were examined, how many contained cancer, the size of the largest deposit, and whether extranodal extension is present, meaning cancer cells have broken through the outer capsule of a node into the surrounding tissue.

Biomarker and molecular testing

Biomarkers are proteins or genetic changes measured in tumor tissue that predict whether a cancer is likely to respond to a particular drug. For intramucosal adenocarcinoma of the esophagus, biomarker testing is usually not performed. These tests exist to guide drug therapy for advanced or metastatic esophageal and gastroesophageal cancer, and a tumor confined to the mucosa is generally cured by local removal without any drug treatment. If your report does not list any of the tests below, that is expected and appropriate.

Biomarker testing becomes relevant if the tumor turns out to be deeper or more extensive than first thought, if cancer returns after treatment, or if disease is found elsewhere in the body. The tests described below are the ones a person with esophageal or gastroesophageal adenocarcinoma is most likely to encounter in those situations. Testing is usually performed by immunohistochemistry or by next generation sequencing, a method that reads many genes at once.

HER2

HER2 is a protein on the surface of cells that signals them to grow and divide. Some esophageal and gastroesophageal adenocarcinomas make far too much of it, usually because the tumor carries extra copies of the ERBB2 gene. HER2 testing begins with immunohistochemistry, and results are reported as a score:

HER2 0 or 1+ (negative) — Little or no HER2 protein is present. HER2-targeted drugs are not expected to work, and no further HER2 testing is done.
HER2 2+ (equivocal) — An intermediate amount of protein is present. A second test, in situ hybridization (usually FISH), is performed to count the copies of the ERBB2 gene and classify the result as amplified (positive) or not amplified (negative).
HER2 3+ (positive) — A strong, uniform amount of HER2 protein is present. No confirmatory test is needed.

A positive result indicates eligibility for HER2-targeted therapy in advanced disease, including trastuzumab combined with chemotherapy in the first-line setting and trastuzumab deruxtecan later on. Pembrolizumab may be added for HER2-positive tumors that also express PD-L1. The scoring criteria used for esophageal and gastric tumors differ slightly from those used in breast cancer, so a score cannot be compared across cancer types.

PD-L1

PD-L1 is a protein that some tumors display on their surface to switch off immune cells that would otherwise attack them. Drugs called immune checkpoint inhibitors block this signal. PD-L1 is measured by immunohistochemistry and reported as a Combined Positive Score (CPS), which counts the number of tumor cells and nearby immune cells showing PD-L1 for every 100 tumor cells.

CPS less than 1 (PD-L1 negative) — Very few cells show PD-L1. Checkpoint inhibitors are not expected to add meaningful benefit, and in 2025 the approvals for pembrolizumab and nivolumab in gastroesophageal cancers were narrowed to exclude this group.
CPS 1 or higher (PD-L1 positive) — Enough cells show PD-L1 to meet the minimum threshold for checkpoint inhibitor eligibility in advanced disease.
CPS 5 or higher, or CPS 10 or higher — Higher scores predict greater benefit, and some approvals and treatment pathways use these higher thresholds. The exact cut-off depends on the drug, the tumor type, and the treatment setting.

PD-L1 testing is performed only when the cancer is advanced, recurrent, or metastatic. It is not part of the workup of a tumor confined to the mucosa.

Mismatch repair (MMR) and microsatellite instability (MSI)

Mismatch repair is the cell’s system for correcting copying errors in DNA. Four proteins do most of this work: MLH1, PMS2, MSH2, and MSH6. Immunohistochemistry is used to check whether each is present.

MMR proficient (pMMR) — All four proteins are present. Your report may use the words retained, intact, preserved, or no loss of nuclear expression. The equivalent molecular result is microsatellite stable (MSS). This is the normal, and by far the most common, result in esophageal adenocarcinoma.
MMR deficient (dMMR) — One or more of the four proteins is absent, described as loss of expression. The equivalent molecular result is microsatellite instability-high (MSI-high).

A deficient result carries two implications. First, it indicates eligibility for immunotherapy: pembrolizumab is approved for dMMR or MSI-high cancers regardless of where in the body the cancer started. Second, it raises the possibility of Lynch syndrome, an inherited condition that increases the risk of several cancers and affects blood relatives. When MLH1 and PMS2 are the proteins lost, additional testing for MLH1 promoter hypermethylation is usually performed first, because that change explains most cases and points to a non-inherited cause. If an inherited cause remains possible, referral for genetic counseling is offered.

Claudin 18.2

Claudin 18.2 is a protein that helps seal the junctions between cells lining the stomach. It is not normally present in the esophagus, but adenocarcinomas arising near the gastroesophageal junction often make it. It is measured by immunohistochemistry.

Claudin 18.2 positive — At least 75% of tumor cells show moderate to strong staining around their outer edge. This indicates eligibility for zolbetuximab, an antibody given with chemotherapy for advanced HER2-negative gastric and gastroesophageal junction adenocarcinoma.
Claudin 18.2 negative — Fewer than 75% of tumor cells stain at that intensity. Zolbetuximab is not expected to be effective, and other treatment pathways are considered.

Not every case requires every one of these tests. A report that lists only some of them, or none at all, is not incomplete. Which tests are ordered depends on the stage of the cancer and on what treatment decisions are being made. You can read more about these and other tests in our Biomarkers and Genetic Testing section.

Pathologic stage (pTNM)

Pathologic stage describes how far an intramucosal adenocarcinoma of the esophagus has grown and whether it has spread. It uses the TNM system of the American Joint Committee on Cancer (AJCC), 8th edition, which remains the current edition for cancers of the esophagus. T describes how deeply the tumor has grown into the wall, N describes whether cancer is found in nearby lymph nodes, and M describes spread to distant organs. The letter p means the stage was determined by examining tissue under the microscope. M is assessed by imaging rather than by pathology, so it does not normally appear on the pathology report.

Tumor stage (pT)

pTis — High-grade dysplasia. Abnormal cells are confined within the glands and have not begun to invade.
pT1a — The tumor has grown into the lamina propria or the muscularis mucosae but not beyond the mucosa. This is the stage of intramucosal adenocarcinoma.
pT1b — The tumor has grown into the submucosa.
pT2 — The tumor has grown into the muscularis propria, the thick muscle layer of the esophageal wall.
pT3 — The tumor has grown through the muscle layer into the surrounding connective tissue.
pT4 — The tumor has grown into neighboring structures such as the diaphragm, the pleura lining the lung, the airway, or the aorta.

Nodal stage (pN)

pN0 — No cancer was found in any of the lymph nodes examined.
pN1 — Cancer was found in one or two lymph nodes.
pN2 — Cancer was found in three to six lymph nodes.
pN3 — Cancer was found in seven or more lymph nodes.
pNX — No lymph nodes were submitted for examination. This is the usual result after an endoscopic resection, because the procedure does not remove lymph nodes.

An intramucosal adenocarcinoma that is completely removed with no evidence of spread is stage IA disease, the earliest stage of invasive esophageal cancer.

What is the prognosis for intramucosal adenocarcinoma of the esophagus?

The prognosis for intramucosal adenocarcinoma of the esophagus is excellent. When the tumor is completely removed through the endoscope with clear margins and no high-risk features, long-term cancer-specific survival exceeds 90%, and outcomes are comparable to those achieved by removing part of the esophagus surgically, without the recovery and long-term effects of that operation. Because the mucosa contains few lymphatic channels, only about 2% to 4% of these tumors have reached the lymph nodes at the time of diagnosis.

The following findings on your pathology report are associated with a higher risk that cancer cells have spread beyond the esophagus, and may lead the treatment team to recommend closer follow-up or additional treatment:

Lymphovascular invasion — The strongest single predictor of lymph node involvement in early esophageal adenocarcinoma.
Poorly differentiated (high grade) tumor — Roughly doubles the likelihood of lymph node involvement compared with well or moderately differentiated tumors.
Positive deep margin — Suggests the tumor may not have been completely removed and may extend deeper than the specimen shows.
Larger tumor size — Tumors 2 cm or larger carry somewhat higher risk than smaller ones.
Invasion into the muscularis mucosae rather than the lamina propria — Associated with a modestly higher risk of spread, although both remain within the pT1a category.

The most common long-term concern after successful treatment is not the tumor that was removed but the Barrett esophagus that remains. New areas of dysplasia or cancer can develop elsewhere in that lining over the following years, which is why the remaining Barrett segment is usually treated and why long-term endoscopic surveillance is recommended.

What happens after this diagnosis?

After intramucosal adenocarcinoma of the esophagus is confirmed, the pathology report is reviewed alongside the endoscopy findings and imaging, usually by a multidisciplinary team that includes gastroenterology, thoracic surgery, pathology, radiology, and medical and radiation oncology. The specific findings on the report guide what the team considers next.

When the tumor has been completely removed, the deep margin is negative, there is no lymphovascular invasion, and the tumor is well or moderately differentiated, endoscopic treatment alone is generally considered sufficient. The next step is usually endoscopic eradication therapy of the remaining Barrett segment, most often radiofrequency ablation or cryotherapy, which destroys the residual abnormal lining and substantially lowers the chance that a new cancer will develop there. Ongoing acid suppression, typically with a proton pump inhibitor, is used to reduce further damage from reflux.

When the report shows lymphovascular invasion, a poorly differentiated tumor, or a positive deep margin, the risk of lymph node involvement is higher, and the team may discuss a repeat endoscopic resection, surgical removal of part of the esophagus with the nearby lymph nodes, or chemotherapy and radiation. Which of these is appropriate depends on the specific combination of findings, on other health conditions, and on the person’s own priorities, and is a decision made together with the treatment team.

Regardless of which path is taken, follow-up endoscopy with biopsies is scheduled at regular intervals for several years, with periodic CT imaging in higher-risk cases. Because reflux and Barrett esophagus persist after treatment, ongoing management of reflux is part of long-term care.

Questions to ask your doctor

Was my tumor completely confined to the mucosa (pT1a), or did it reach the submucosa?
Was the tumor removed in one piece, or in fragments?
Were the deep and lateral margins negative, and how close was the tumor to the edge?
Was lymphovascular invasion present?
What was the histologic grade of my tumor?
Based on these findings, what is my estimated risk that cancer has spread to lymph nodes?
Do I need any further treatment beyond the endoscopic resection?
Will the remaining Barrett esophagus be treated with ablation, and how many sessions might that take?
Was my case reviewed by a second pathologist or a multidisciplinary tumor board?
How often will I need follow-up endoscopy, and for how many years?
Will I need CT scans or other imaging as part of follow-up?
What medication should I take for reflux, and will I need it long term?
Were any biomarker tests performed on my tumor, and if not, why not?
Should any of my family members be screened for Barrett esophagus?