What is stomach (gastric) cancer?
The stomach stores and digests food before it passes into the small intestine. Most cancers arising there are adenocarcinomas, but lymphomas, gastrointestinal stromal tumors, neuroendocrine tumors, and rare cancers require different treatment pathways. Helicobacter pylori infection, chronic inflammation, smoking, family history, some inherited syndromes, and certain dietary or medical factors can increase risk. Tumors near the gastroesophageal junction may be classified and treated according to their exact location. Early gastric cancer may remain within superficial wall layers; more advanced disease can grow through the stomach wall, reach regional lymph nodes, involve the peritoneum, or spread to organs such as the liver. Diffuse-type cancers, including hereditary diffuse gastric cancer, may grow without forming a single obvious mass. Because both the disease and treatment can affect eating, nutrition assessment is part of care. Biomarker testing now helps choose therapy for many advanced gastric adenocarcinomas.
Signs and symptoms
Early stomach cancer may cause indigestion, stomach discomfort, bloating after meals, mild nausea, reduced appetite, or heartburn, and some people have no symptoms. More advanced disease may cause persistent abdominal pain, vomiting, blood in vomit, black stools, unexplained weight loss, difficulty swallowing, marked tiredness from anemia, or fluid buildup in the abdomen. Feeling full after a small meal can interfere with nutrition, and a slow blood loss may first appear as fatigue or shortness of breath. These symptoms can have noncancer causes, including ulcers, reflux, gastritis, infection, medication effects, or gallbladder and pancreatic disease. Persistent, progressive, bleeding-related, or otherwise unexplained symptoms need medical assessment. Vomiting blood, passing black stools, severe weakness, or inability to keep down fluids requires prompt care.
Diagnosis and staging
Upper endoscopy allows direct inspection of the stomach and biopsy of abnormal tissue; pathology establishes cancer type and may evaluate key biomarkers. Blood tests can identify anemia and assess organ function. CT imaging stages the chest, abdomen, and pelvis. Endoscopic ultrasound can estimate how deeply a tumor enters the stomach wall and sample nearby nodes. PET may help selected cases, while diagnostic laparoscopy and peritoneal washings can find small-volume abdominal spread that scans miss, particularly before curative-intent surgery. TNM staging describes depth of invasion, regional lymph nodes, and distant metastases, grouped from stage 0 through IV. Advanced adenocarcinoma testing commonly includes HER2, PD-L1, mismatch-repair or microsatellite-instability status, and sometimes CLDN18.2 or broader genomic profiling. Germline genetic evaluation may be appropriate when age, family history, or tumor pattern suggests an inherited syndrome. Care depends on location, histology, stage, biomarkers, nutrition, overall health, and treatment goals.
Established treatment paths
Very early cancers limited to the stomach lining may be removed endoscopically when strict pathologic criteria are met. Resectable cancers are generally treated with removal of part or all of the stomach plus regional lymph nodes. Chemotherapy before and after surgery is common for many localized adenocarcinomas; postoperative chemotherapy or chemoradiation may be considered based on prior treatment, pathology, and surgical approach. Unresectable or metastatic disease is treated with systemic therapy. Regimens can combine chemotherapy with immunotherapy or targeted treatment according to HER2, PD-L1, mismatch-repair or microsatellite-instability status, CLDN18.2, prior therapy, and patient factors. Repeat biomarker testing can sometimes be useful because tumor features may change after treatment. Radiation can help control a local tumor or relieve bleeding, pain, or obstruction. Endoscopic stents, bypass procedures, feeding access, or other interventions may restore passage of food when needed. Tumors such as gastric lymphoma or gastrointestinal stromal tumor follow different protocols. Clinical trials may provide additional options. Treatment depends on histology, stage, biomarkers, fitness, nutrition, prior therapy, preferences, and treatment response.
Supportive care
Nutrition support is central because cancer, obstruction, gastrectomy, and systemic therapy can reduce intake or absorption. An oncology dietitian can help with small frequent meals, protein and calorie needs, dumping symptoms, and vitamin or mineral replacement; vitamin B12 may require long-term monitoring after some operations. Antiemetics, pain control, fatigue management, and treatment of anemia can improve daily function. Swallowing or obstruction symptoms may require urgent reassessment. Palliative care can support symptom control and decisions at any stage. Follow-up should monitor recurrence, weight, and postoperative nutritional consequences.
Profiles documenting stomach (gastric) cancer care
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Sources
Source information checked: 2026-09-29. The links below identify the public and clinic-provided materials used for this page.
- NCI: What Is Stomach Cancer? ↗Checked 2026-09-29
- NCI: Stomach Cancer Treatment ↗Checked 2026-09-29
- NCI: Stomach Cancer Treatment by Stage ↗Checked 2026-09-29
- NCI: Nutrition During Cancer ↗Checked 2026-09-29
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