Intramucosal Adenocarcinoma of the Stomach: Understanding Your Pathology Report

by Jason Wasserman MD PhD FRCPC
July 31, 2026

Intramucosal adenocarcinoma of the stomach is an early cancer that begins in the glandular cells lining the stomach, the cells that normally produce mucus and digestive juices. The word intramucosal means the cancer is still confined to the mucosa, the thin innermost lining of the stomach, and has not grown into the deeper layers of the stomach wall.

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

Your report may describe this diagnosis in several ways: intramucosal adenocarcinoma, intramucosal carcinoma, adenocarcinoma with invasion limited to the mucosa, adenocarcinoma pT1a, or early gastric cancer. 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 stomach?

Intramucosal adenocarcinoma of the stomach usually develops at the end of a long sequence of changes in the stomach lining that unfolds over decades. The most common driver is chronic infection with Helicobacter pylori, a bacterium that causes long-standing inflammation of the lining. Over many years this inflammation can lead to atrophy, meaning loss of the normal stomach glands, then to intestinal metaplasia, in which the stomach lining is replaced by cells resembling those of the intestine, then to dysplasia, and finally to cancer.

Other factors that raise the risk include:

Diet — High intake of salt-preserved, pickled, or smoked foods, and low intake of fresh fruits and vegetables.
Smoking — An independent risk factor at every step of the sequence.
Autoimmune gastritis and pernicious anemia — Conditions in which the immune system attacks the stomach lining, producing atrophy without H. pylori.
Family history — Having a first-degree relative with stomach cancer.
Previous stomach surgery — Which changes the environment of the remaining lining.

Because the background lining matters, your report will often describe it alongside the tumor, noting whether atrophy, intestinal metaplasia, or active H. pylori infection is present. These findings are not incidental. They indicate how much of the remaining stomach is at risk, and they shape how closely you are followed afterward.

What are the symptoms of intramucosal adenocarcinoma of the stomach?

Intramucosal adenocarcinoma of the stomach usually causes no symptoms of its own. It is small, confined to the surface lining, and does not block or distort the stomach.

In countries with screening programs, most cases are found during a routine endoscopy in someone without complaints. Elsewhere, they are usually discovered incidentally during an endoscopy performed for indigestion, reflux, or anemia. When symptoms are present they are vague and come from the underlying gastritis rather than the tumor: mild upper abdominal discomfort, indigestion, bloating, or nausea. Unexplained weight loss, vomiting, difficulty swallowing, or signs of bleeding are not features of intramucosal cancer, and when present they suggest a deeper or more extensive tumor.

How is the diagnosis made?

The diagnosis of intramucosal adenocarcinoma of the stomach is made only after tissue from the stomach is examined under a microscope by a pathologist. The tissue is obtained during an upper endoscopy, in which a thin flexible tube with a camera is passed through the mouth so the lining can be inspected.

These cancers are easy to miss. They are often flat or only slightly raised or sunken, and may show only a subtle change in color or in the pattern of surface blood vessels. Endoscopists use high-definition cameras, narrow band imaging, and sometimes a dye sprayed onto the lining to make the edges of the abnormal area visible. Defining those edges accurately matters, because the whole lesion needs to be removed in one piece.

A small biopsy can show that cancer is present, but it cannot show how deep it goes, because the deeper layers of the stomach wall are not included in the sample. For this reason an endoscopic resection usually follows a biopsy diagnosis. The procedure most often used is endoscopic submucosal dissection, in which the lesion is lifted and dissected away in a single piece. Removing it whole both treats the cancer and provides the complete, properly oriented specimen the pathologist needs to answer the questions described in the rest of this article.

Under the microscope, the pathologist looks for glands that are crowded, fused, or growing back-to-back, and for tumor cells growing directly into the surrounding tissue of the lamina propria, the supportive layer within the mucosa. Critically, the pathologist confirms that this growth does not reach the submucosa, the layer beneath the mucosa.

One point of terminology is worth understanding, because it can lead to two apparently different diagnoses on the same tissue. Pathologists in Japan diagnose intramucosal carcinoma based on how abnormal the cells and glands look, without requiring clear evidence of invasion. Pathologists in North America and Europe have traditionally required visible invasion into the lamina propria, and call the same appearance high grade dysplasia when invasion cannot be demonstrated. If you obtain a second opinion and receive a different label, this difference in convention is the usual explanation rather than an error. Practically, the two are managed the same way: both are removed endoscopically and followed afterward.

Histologic type

Histologic type describes how the cancer cells of an intramucosal adenocarcinoma are arranged. For an endoscopically removed stomach cancer, the type is grouped into two categories, and this grouping matters more here than anywhere else in stomach cancer because it directly affects whether the endoscopic removal is considered sufficient.

Differentiated type — The tumor forms recognizable glands. This includes tubular and papillary adenocarcinoma and covers the large majority of cases. These tumors spread to lymph nodes less readily at this depth.
Undifferentiated type — The tumor forms few or no glands, and includes poorly cohesive carcinoma and signet ring cell carcinoma. These tumors carry a somewhat higher risk of lymph node involvement, so the size and other criteria for treating them endoscopically are stricter.

Some tumors contain both patterns, and the report will state which one predominates. This “differentiated versus undifferentiated” grouping comes from the Japanese classification system used to guide endoscopic treatment, and it sits alongside rather than replaces the World Health Organization type your report may also name.

Histologic grade

Grade describes how closely the cancer cells in an intramucosal adenocarcinoma resemble normal stomach cells, based on how much of the tumor still forms glands.

Grade 1 (well differentiated) — More than 95% of the tumor forms glands.
Grade 2 (moderately differentiated) — Between 50% and 95% of the tumor forms glands.
Grade 3 (poorly differentiated) — Less than 50% of the tumor forms glands.

Grade and histologic type overlap considerably: grade 1 and grade 2 tumors are generally differentiated type, and grade 3 tumors generally undifferentiated type. Grade is included on the report for completeness, but for a tumor removed endoscopically it is the type, together with size, ulceration, depth, and margins, that determines what happens next.

Depth of invasion

Depth of invasion describes how far an intramucosal adenocarcinoma has grown into the wall of the stomach, and it is the most important single finding. The stomach wall is built in layers. The mucosa, the innermost lining, contains the surface and glandular cells, the lamina propria, and a thin band of muscle at its base called the muscularis mucosae. Beneath it lies the submucosa, which carries the larger blood vessels and lymphatic channels, then the thick muscle layer, and finally the outer surface.

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 elsewhere. This is why it can usually be cured by removing the affected patch of lining alone.

If the tumor has reached the submucosa, the report will say so and will give the depth in micrometers measured from the muscularis mucosae. That number matters: invasion of less than 500 micrometers is treated differently from invasion of 500 micrometers or more, because the risk of lymph node spread rises at that threshold.

Tumor size and ulceration

Two further measurements appear on the report for an intramucosal adenocarcinoma, and both feed directly into whether the endoscopic removal is considered sufficient.

Tumor size — The greatest dimension of the cancer, in millimeters. Larger tumors carry a modestly higher risk of lymph node involvement, and size thresholds of 20 mm and 30 mm are used in the criteria described below.
Ulceration — Whether an ulcer, or a scar from a previous ulcer, is present within the tumor. Your report may record this as UL0 (absent) or UL1 (present). Ulceration raises the risk of lymph node involvement and also makes the lesion harder to remove cleanly, because scarring tethers the lining to the layers beneath.

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.

It is uncommon in tumors confined to the mucosa, but when found it is the strongest single indicator that cancer cells may have reached the lymph nodes. Its presence alone is enough to make an otherwise ideal endoscopic removal insufficient, and it usually prompts a discussion of surgery. Where the finding is difficult to judge, immunohistochemical stains that highlight the lining of 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. It is reported as present or absent.

Nerves lie mostly in the deeper layers of the stomach 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.

Margins

A margin is the cut edge of the tissue removed. For an endoscopic resection the pathologist inks these edges and examines two of them:

Horizontal (lateral) margin — The side edges of the removed disc of lining. A positive horizontal margin means abnormal tissue may remain in the surrounding lining, raising the risk that cancer will regrow at the same site.
Vertical (deep) margin — The deepest cut surface, beneath the tumor. This is the more important of the two, because a positive vertical margin raises the possibility that the tumor was cut across at its base and extends deeper than the specimen shows.

The report will also state whether the lesion was removed in one piece, described as en bloc, or in several fragments, described as piecemeal. This matters as much as the margin result itself: when a lesion comes out in pieces, the fragments cannot always be fitted back together, and the margins may be impossible to assess reliably. This is one reason endoscopic submucosal dissection, which removes the lesion whole, is preferred over older techniques.

Curability after endoscopic resection

After an intramucosal adenocarcinoma is removed endoscopically, all of the findings above are combined into a single judgment: whether the removal is likely to have cured the cancer, or whether further treatment should be discussed. Many reports record this using a system known as endoscopic curability, or eCura, and the category may appear directly on your report.

eCura A — The removal meets all criteria for cure. The tumor was confined to the mucosa, removed in one piece with clear horizontal and vertical margins, and showed no lymphovascular invasion, and it was either differentiated type without ulceration at any size, differentiated type with ulceration and 30 mm or smaller, or undifferentiated type without ulceration and 20 mm or smaller. In large studies the risk of lymph node involvement in this group has been essentially zero, and no further treatment is needed.
eCura B — A differentiated-type tumor that has just entered the submucosa (less than 500 micrometers), 30 mm or smaller, with clear margins and no lymphovascular invasion. The risk of lymph node involvement is also very low, and this is likewise considered a curative removal.
eCura C-1 — The tumor would have met the criteria above, but it was removed in pieces or the horizontal margin was positive. The risk of lymph node involvement remains very low; the concern is that tumor may remain at the original site. Options include a repeat endoscopic resection, surgery, or close endoscopic follow-up.
eCura C-2 — The removal does not meet the criteria above, most often because of lymphovascular invasion, deeper submucosal invasion, a positive vertical margin, or an undifferentiated tumor outside the size limits. Surgery to remove part of the stomach with the nearby lymph nodes is generally recommended.

Two things are worth knowing about the eCura C-2 category. First, roughly 15% to 20% of endoscopic resections turn out not to meet the curative criteria, so this is a common outcome rather than an unusual one. Second, even within this group only about 8% of people are found to have cancer in their lymph nodes at surgery. A scoring system that weighs the individual findings, particularly lymphovascular invasion, can estimate that risk more precisely, and for some people, especially those for whom surgery carries significant risk, careful follow-up is a reasonable alternative. This is a decision made together with the treatment team rather than an automatic one.

Lymph nodes

Lymph nodes are small immune organs found around the stomach. Cancer cells can travel to them through lymphatic channels, and cancer found in a lymph node is a form of metastasis.

Most people with intramucosal adenocarcinoma will not see lymph nodes mentioned on their report at all. Endoscopic resection removes only the inner lining and does not include lymph nodes, so there are none to examine. This is not an omission. It reflects the fact that cancer confined to the mucosa, without ulceration or lymphovascular invasion, spreads to lymph nodes in well under 1% of cases, which is why removing lymph nodes is unnecessary for most people.

If part of the stomach is removed surgically, lymph nodes are taken at the same time, and the report will state how many were examined and how many contained cancer.

Biomarker and molecular testing

Biomarkers are proteins or genetic changes measured in tumor tissue that predict whether a cancer will respond to a particular drug. For intramucosal adenocarcinoma of the stomach, biomarker testing is usually not performed. Tests such as HER2, PD-L1, claudin 18.2, and mismatch repair guide drug treatment for advanced stomach 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 these tests, that is expected and appropriate rather than a sign that something was missed. Testing becomes relevant only if the tumor turns out to be deeper or more extensive than first thought, if cancer returns, or if disease is found elsewhere. You can read about these tests in our article on adenocarcinoma of the stomach and in the Biomarkers and Genetic Testing section.

Pathologic stage (pTNM)

Pathologic stage describes how far an intramucosal adenocarcinoma of the stomach has grown and whether it has spread. It uses the TNM system of the American Joint Committee on Cancer (AJCC), 8th edition. 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.

Tumor stage (pT)

pTis — High grade dysplasia, also called carcinoma in situ. 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 remains within the mucosa. This is the stage of intramucosal adenocarcinoma.
pT1b — The tumor has grown into the submucosa.
pT2 — The tumor has grown into the main muscle layer of the stomach wall.
pT3 — The tumor has grown through the muscle layer into the connective tissue beneath the outer surface.
pT4a — The tumor has broken through the outer surface of the stomach.
pT4b — The tumor has grown directly into a neighboring organ or structure.

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 completely removed with no evidence of spread is stage IA, the earliest stage of stomach cancer.

What is the prognosis for intramucosal adenocarcinoma of the stomach?

The prognosis for intramucosal adenocarcinoma of the stomach is excellent. After a curative endoscopic removal, long-term survival from this cancer is roughly 99% at five years and 93% at ten years, and outcomes are comparable to those achieved by removing part of the stomach surgically, without the permanent changes to eating and nutrition that operation brings.

For a differentiated-type tumor confined to the mucosa, without ulceration and without lymphovascular invasion, the risk that cancer has already reached the lymph nodes is well under 1%. That figure is the foundation of the whole approach of treating these cancers through the endoscope.

Findings on your report associated with a higher risk of lymph node involvement, and therefore of needing further treatment, are lymphovascular invasion, undifferentiated histologic type, ulceration within the tumor, larger tumor size, invasion reaching the submucosa, and a positive vertical margin.

The main long-term concern after successful treatment is not the tumor that was removed but the rest of the stomach lining, which usually carries the same atrophy and intestinal metaplasia that produced the first cancer. A new, separate cancer develops elsewhere in the stomach in roughly 2% to 3% of people per year, and that risk continues for at least a decade. This is the reason lifelong endoscopic follow-up is recommended even after a complete cure.

What happens after this diagnosis?

Once an intramucosal adenocarcinoma of the stomach has been removed and the pathology report is complete, the findings are reviewed by a team that generally includes gastroenterology, surgery, and pathology. The curability category described above determines what follows.

When the removal meets the criteria for cure, no further cancer treatment is needed. When it does not, the team discusses whether a repeat endoscopic resection, surgery to remove part of the stomach with the nearby lymph nodes, or continued close follow-up is the better course, weighing the estimated risk of lymph node involvement against the risks of surgery and the person’s own priorities.

Two further steps apply to nearly everyone. If H. pylori is present, it is treated and the eradication is confirmed afterward with a breath or stool test. This is not simply tidying up an infection: eradication roughly halves the chance of a new stomach cancer developing later, and it is one of the most effective things that can be done after treatment. Second, surveillance endoscopy is scheduled, usually annually and continuing indefinitely, because new cancers keep appearing at a steady rate for many years and are highly curable when caught early.

Where the background lining shows extensive atrophy and intestinal metaplasia, follow-up may be more intensive, and first-degree relatives are sometimes offered screening depending on family history and background risk.

Questions to ask your doctor

Was my tumor completely confined to the mucosa (pT1a), or did it reach the submucosa?
Was the lesion removed in one piece, or in fragments?
Were the horizontal and vertical margins negative?
Was lymphovascular invasion present?
Was my tumor differentiated or undifferentiated type, and how large was it?
Was there an ulcer or ulcer scar within the tumor?
What was my endoscopic curability category, and what does it mean for my treatment?
Based on these findings, what is my estimated risk that cancer has reached the lymph nodes?
Do I need surgery, a repeat endoscopic resection, or is follow-up alone appropriate?
Did my biopsies show H. pylori, and will the eradication be confirmed with a follow-up test?
Does my report describe atrophy or intestinal metaplasia in the rest of my stomach, and does that change my follow-up?
How often will I need surveillance endoscopy, and for how long?
What is my risk of developing a new stomach cancer in the future?
Should any of my family members be screened?