Stomach (gastric) cancer occurs when cells in the stomach grow out of control. It usually begins in the innermost lining (the mucosa) and can grow deeper into the stomach wall over time, and it tends to develop slowly. The most common type is adenocarcinoma, which arises from the gland cells of the stomach lining.
Gastric dysplasia is a precancerous change, meaning abnormal cells are present in the stomach lining but have not become invasive cancer. It is graded as low-grade dysplasia (milder cellular abnormality) or high-grade dysplasia (more severe abnormality that carries a higher likelihood of coexisting or developing cancer).
Stomach cancer often develops through a recognised step-by-step sequence, sometimes called the Correa cascade: chronic inflammation of the stomach lining (gastritis), followed by thinning of the lining (atrophic gastritis), then a change to intestinal-type cells (intestinal metaplasia), then dysplasia, and finally cancer. Chronic infection with the bacterium Helicobacter pylori is the typical trigger of this pathway. It is important to understand that not everyone with these precancerous changes goes on to develop cancer; the sequence describes increased risk, not an inevitable outcome.
Early stomach cancer often causes no symptoms, and many signs appear only once the disease is more advanced. When symptoms do occur, they may include:
- Indigestion or heartburn
- Pain in the upper abdomen
- Feeling full after eating only a small amount (early satiety)
- Loss of appetite
- Nausea and vomiting
- Unexplained weight loss
- Bloating after eating
- Difficulty swallowing
- Fatigue or weakness, which may be due to anemia
- Black stools or vomiting blood, which are signs of bleeding
Many of these symptoms overlap with far more common, benign conditions and are not specific to cancer.
Causes and Risk Factors
Stomach cancer develops after changes in the DNA of stomach cells, but the precise trigger is often unknown. Established risk factors include:
- Helicobacter pylori infection — a major cause, particularly of cancers in the lower part of the stomach; most infected people never develop cancer
- Chronic atrophic gastritis, including the autoimmune form
- A diet high in salt-preserved, smoked or pickled foods and low in fruit and vegetables
- Smoking and other tobacco use
- Alcohol, with the strongest evidence at higher intake levels
- A family history of stomach cancer
- Inherited syndromes, such as hereditary diffuse gastric cancer, Lynch syndrome and familial adenomatous polyposis
- Pernicious anemia
- Previous stomach surgery, with cancers typically arising many years later
- Epstein-Barr virus infection
- Obesity
- Older age and male sex
Diagnosis
Diagnosis begins with a review of symptoms and a physical examination, followed by tests that may include:
- Upper endoscopy with biopsy — the main method, in which a thin scope inspects the stomach lining and takes tissue samples
- Histology — examination of the biopsy under the microscope to determine the grade of dysplasia or the presence of cancer
- Endoscopic ultrasound — to assess how deeply a tumour has grown into the stomach wall
- Imaging such as CT, MRI or PET scans — to detect tumours and any spread
- Laparoscopy — direct visualisation used when imaging is inconclusive
- Helicobacter pylori testing — recommended, with eradication advised when the infection is found alongside gastritis or precancerous changes
Staging ranges from stage 0, where disease is confined to the lining, to stage IV, where it has spread to other organs.
Treatment and Management
Treatment depends on the stage of disease and is usually planned by a multidisciplinary team.
Dysplasia and Very Early Cancer
- Low-grade dysplasia — surveillance endoscopy with repeat biopsy is commonly used
- High-grade dysplasia and early cancer confined to the surface layers — endoscopic resection (endoscopic mucosal resection or endoscopic submucosal dissection) can remove the lesion through the endoscope
Invasive Cancer
- Surgery — partial or total removal of the stomach (gastrectomy) along with nearby lymph nodes; palliative procedures may relieve blockage in advanced cases
- Chemotherapy — given before or after surgery, or for more advanced disease
- Radiation therapy — sometimes used together with chemotherapy or to relieve symptoms
- Targeted therapy — medicines directed at specific features of the cancer, such as HER2, guided by testing of the tumour
- Immunotherapy — used in selected cases, guided by biomarker testing
Palliative care can be provided alongside any treatment to manage symptoms and support quality of life.
Prognosis
The outlook for stomach cancer depends strongly on the stage at which it is found. Early-stage disease has a much better prognosis and can be curable, while advanced disease that has spread has a poorer outlook. Because symptoms often appear late, many cases are diagnosed at a more advanced stage, which is why prompt evaluation of persistent symptoms matters. Survival figures vary widely according to how far the cancer has spread, and an individual assessment by a specialist is the most reliable guide.
Prevention
The risk of stomach cancer can be reduced by:
- Testing for and treating Helicobacter pylori infection, which lowers risk especially in higher-risk people
- Treating gastritis, ulcers and other stomach conditions promptly
- Eating a diet rich in fruit and vegetables and low in salt-preserved and processed foods
- Avoiding tobacco and limiting alcohol
- Maintaining a healthy weight
Stomach cancer cannot always be prevented, but these measures and early detection make a meaningful difference.
When to See a Doctor
See a doctor for persistent stomach pain or unexplained weight loss, particularly when accompanied by:
- Difficulty eating or swallowing
- Persistent nausea or vomiting
- Vomiting blood or black, tarry stools
- Ongoing indigestion or early fullness that does not settle
- Fatigue that may reflect anemia
People at increased risk, such as those with a family history, a known hereditary syndrome or precancerous changes, should discuss surveillance with their doctor. Most of these symptoms have benign causes, but only a doctor can determine the cause, so timely evaluation is what matters.