The short answer
Stomach cancer, also called gastric cancer, starts in the cells lining the stomach. The stomach is a digestive organ in the upper left abdomen. Nearly all stomach cancers are adenocarcinomas, which begin in the mucus-making cells of the stomach lining. Doctors also describe stomach cancer by where in the stomach it forms.
Stomach (gastric) cancer starts in the cells lining the stomach.
The stomach is part of the digestive tract and helps break down food.
Nearly all stomach cancers are adenocarcinomas, which begin in the mucus-producing cells of the innermost lining.
Adenocarcinoma is grouped as gastric cardia cancer (near the esophagus) or non-cardia cancer (elsewhere in the stomach).
Subjective: What you might experience
This section describes the symptoms and history a patient might report to their doctor.
Indigestion, heartburn, or stomach discomfort that persists.
Feeling full after eating only a small amount.
Nausea, vomiting (sometimes with blood), and loss of appetite.
Unexplained weight loss and fatigue (sometimes from anemia).
Black or bloody stools.
Risk history
H. pylori infection, smoking, diet, chronic stomach inflammation, and family history.
Objective: Tests and findings
Upper endoscopy (EGD) to view the stomach lining and take biopsies — the key test.
Biopsy for tissue diagnosis, with HER2 and PD-L1 testing when relevant.
Endoscopic ultrasound to assess depth of invasion and nearby nodes.
CT of chest/abdomen/pelvis and PET to evaluate spread.
Testing for H. pylori and blood counts.
Interactive anatomy guide
Explore where cancers start and how they are found, on an interactive body map.
Open the anatomy guideAssessment: Staging and prognosis
Most are adenocarcinomas; diagnosis confirmed by biopsy.
Staged with the TNM system based on depth of invasion, nodes, and metastasis.
Biomarkers (HER2, MSI, PD-L1) guide therapy in advanced disease.
Sometimes staging laparoscopy is used to check for spread on the abdominal lining.
Plan: The treatment approach
Surgery to remove part or all of the stomach with nearby lymph nodes for localized disease.
Chemotherapy before and/or after surgery, sometimes with radiation.
Advanced disease
chemotherapy, targeted therapy (e.g., HER2), immunotherapy, and clinical trials.
H. pylori treatment and nutritional support.
Follow-up endoscopy and imaging.
These are simplified, educational SOAP-style summaries showing the kinds of findings clinicians document when evaluating each cancer, based on National Cancer Institute resources. They describe typical diagnostic criteria and workups — not a real patient, and not medical advice. Real clinical notes are individualized. Always rely on your own care team. Based on National Cancer Institute educational content. Educational only — not medical advice.
Words to know
Tap any term to see what it means.
Common questions
What is stomach cancer?
Stomach cancer, also called gastric cancer, is cancer that starts in the cells lining the stomach. The stomach is an organ on the left side of the upper abdomen that digests food. It is part of the digestive tract, a long, twisting tube of hollow, muscular organs that runs from the mouth to the anus.
What does the stomach do?
Food moves from the throat to the stomach through a tube called the esophagus. After food enters the stomach, stomach muscles mix it with digestive juices to break it down. The partly digested food then passes into the small intestine and later the large intestine.
What is the most common type of stomach cancer?
Nearly all stomach cancers are adenocarcinomas. Adenocarcinoma of the stomach begins in the mucus-producing cells in the innermost lining of the stomach.
How is adenocarcinoma of the stomach classified?
It is divided into two main classes based on where it forms. Gastric cardia cancer begins in the top inch of the stomach, just below where it meets the esophagus. Non-cardia gastric cancer begins in all other parts of the stomach. It can also be described as intestinal or diffuse, depending on how the cells look under a microscope.
Are there other types of stomach cancer besides adenocarcinoma?
Yes, but they are less common. Other types include gastrointestinal neuroendocrine tumors, gastrointestinal stromal tumors (GIST), and primary gastric lymphoma. Rarely, other types such as squamous cell carcinoma, small cell carcinoma, and leiomyosarcoma can also begin in the stomach.
What is gastroesophageal junction (GEJ) adenocarcinoma?
Gastroesophageal junction adenocarcinoma is a cancer that forms in the area where the esophagus meets the top of the stomach. It may be treated similarly to stomach cancer or to esophageal cancer.
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Sources last checked: 2026-07-21 what this meansLast updated: 2026-08-10Next planned review: 2027-07-21
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How this page was created
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes. We do not employ clinicians and do not intend to — our work is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and checked line by line against the sources listed on it. That confirms the sources support what the page says. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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