Stomach Cancer: Causes, Symptoms, Types, Diagnosis & Treatment

The stomach is an important part of the digestive system. It stores food, mixes it with digestive juices and helps break it down before it moves into the small intestine. Stomach cancer, also called gastric cancer, develops when abnormal cells in the stomach grow uncontrollably and form a tumour. In some cases, these cancer cells can grow through the stomach wall and spread to nearby lymph nodes or other organs.

Stomach cancer is not a single disease. Most cases are adenocarcinomas, but other less common cancers can also originate in the stomach. The condition may not cause noticeable symptoms in its early stages, which can make timely diagnosis challenging. Understanding the risk factors, warning signs, diagnostic tests and available treatment options can help people seek medical advice at the right time.

What is Stomach Cancer?

Stomach cancer begins when changes in the DNA of stomach cells affect how they grow and divide. Instead of following the normal life cycle of cells, abnormal cells may continue multiplying and form a tumour.

The cancer can develop in different parts of the stomach, including the upper portion near the oesophagus, the main body of the stomach or the lower portion that connects to the small intestine. Its location, depth of growth and whether it has spread are important when doctors determine the stage and treatment approach.

Most stomach cancers are adenocarcinomas, which begin in the gland-forming cells of the stomach lining. Other types include gastrointestinal stromal tumours (GISTs), gastric lymphomas and some rare neuroendocrine or other cancers.

Symptoms of Stomach Cancer

Early disease may cause few or no obvious symptoms. When symptoms do occur, they can resemble common digestive problems such as indigestion or gastritis. This is why persistent or unusual symptoms should not simply be ignored.

Common stomach cancer symptoms may include:

• Persistent indigestion or heartburn
• Pain or discomfort in the upper abdomen
• Feeling bloated after eating
• Feeling full after eating a small amount of food
• Reduced appetite
• Nausea or vomiting
• Difficulty swallowing
• Unintentional weight loss
• Persistent tiredness or weakness
• Vomiting blood
• Black, tarry stools, which may indicate bleeding

These symptoms do not necessarily mean a person has cancer. Several gastrointestinal conditions can cause similar complaints. However, symptoms that persist, worsen or occur alongside unexplained weight loss, bleeding or difficulty swallowing should be assessed by a doctor.

What are the early signs of stomach cancer?

There may be no clear early warning sign. Some people experience mild indigestion, upper abdominal discomfort, bloating or early fullness, while others have no symptoms at all.

This is one reason why persistent digestive symptoms deserve medical attention, particularly in people with known risk factors. The signs of stomach cancer can become more noticeable as the disease progresses, but waiting for severe symptoms is not advisable.

What Causes Stomach Cancer?

There is no single cause of stomach cancer. It develops through changes in stomach cells, while several factors can increase the likelihood of those changes occurring.

Important stomach cancer causes and risk factors include:

Risk factor	How it may increase risk
H. pylori infection	Long-term infection can cause chronic inflammation and changes in the stomach lining, increasing the risk of gastric cancer.
Family history	Having a close relative with stomach cancer can increase risk, particularly when several family members are affected.
Inherited conditions	Conditions such as hereditary diffuse gastric cancer, Lynch syndrome and familial adenomatous polyposis can increase risk.
Chronic stomach inflammation	Conditions such as chronic atrophic gastritis and intestinal metaplasia can cause changes in the stomach lining associated with increased risk.
Tobacco use	Smoking increases the likelihood of developing stomach cancer and can also make H. pylori treatment less effective.
Diet	Frequent consumption of heavily salted, smoked or poorly preserved foods is associated with increased risk, while a diet rich in fruits and vegetables may be protective.
Obesity and GERD	These factors are particularly associated with cancers developing in the upper part of the stomach.
Certain occupational exposures	Long-term exposure in some industries, including rubber and coal-related work, has been associated with higher risk.

Types of Stomach Cancer

The type of cancer is identified through examination of tumour tissue and other diagnostic information.

Gastric adenocarcinoma

This is the most common type and accounts for approximately 90% to 95% of gastric malignancies. It develops from cells in the stomach lining.

Gastrointestinal stromal tumour

GIST is a type of soft-tissue sarcoma that can develop in the digestive tract, including the stomach. It is biologically different from gastric adenocarcinoma and may require different treatments.

Gastric lymphoma

Lymphoma can develop in the stomach as well. MALT lymphoma and diffuse large B-cell lymphoma are among the gastric lymphomas recognised by specialists.

Other rare types

Rare stomach cancers include neuroendocrine tumours, squamous cell carcinoma, small cell carcinoma and leiomyosarcoma. Because these cancers behave differently, treatment depends on the specific diagnosis.

How is Stomach Cancer Diagnosed?

Diagnosis usually begins with a discussion about symptoms, medical and family history and a physical examination. Doctors may also order blood tests to look for anemia or other signs of illness. A stool test may sometimes be used to check for hidden blood.

Test	What it helps doctors understand
Upper endoscopy	Allows the doctor to examine the lining of the oesophagus, stomach and upper small intestine for abnormal areas.
Biopsy	A tissue sample taken during endoscopy is examined under a microscope to confirm whether cancer is present and identify its type.
Blood tests	Can help identify problems such as anaemia, which may occur because of bleeding, and assess overall health.
Endoscopic ultrasound	Helps assess how deeply a tumour has grown into the stomach wall and whether nearby lymph nodes may be involved.
CT or PET-CT scan	Helps determine whether cancer has spread to nearby tissues, lymph nodes or distant organs.
Laparoscopy	In selected cases, allows doctors to examine the abdominal cavity directly and look for cancer spread that may not be obvious on scans.
Biomarker testing	Tests the tumour for markers such as HER2, PD-L1, MSI or mismatch repair deficiency, which can help guide targeted treatment or immunotherapy.

No single test provides all the answers. Endoscopy with biopsy is particularly important for confirming the diagnosis, while imaging and staging tests help determine how far the disease has progressed and which treatment options may be appropriate.

Stages Of Stomach Cancer

Staging describes how far the cancer has progressed. Doctors consider factors such as how deeply the tumour has invaded the stomach wall, whether lymph nodes contain cancer cells and whether the disease has spread to distant organs.

In general, stomach cancer is classified from Stage 0 to Stage IV. Stage 0 refers to abnormal cells limited to the innermost lining, while Stage IV indicates metastatic disease, meaning the cancer has spread to distant parts of the body.

Staging is important because it helps the medical team estimate prognosis and choose the most appropriate treatment.

Stomach Cancer Treatment

The stomach cancer treatment plan depends on the tumour’s type, location and stage, as well as the person’s overall health and preferences. Treatment is often planned by a multidisciplinary team involving specialists such as surgical oncologists, medical oncologists, gastroenterologists, radiologists and pathologists.

Surgery

Surgery may offer the possibility of removing the cancer when it is localised and can be completely removed. For very early cancers confined to the superficial lining, an endoscopic procedure may sometimes remove the abnormal tissue without removing part of the stomach.

For cancers that extend deeper, doctors may recommend a partial or total gastrectomy. A partial gastrectomy removes part of the stomach, while a total gastrectomy removes the entire stomach and reconnects the oesophagus to the small intestine. Nearby lymph nodes may also be removed and examined.

Chemotherapy

Chemotherapy uses medicines that travel through the bloodstream to destroy or slow the growth of cancer cells. Depending on the stage, chemotherapy may be given before surgery to shrink the tumour, after surgery to reduce the risk of recurrence, or as part of treatment for advanced disease.

Radiation therapy

Radiation therapy uses high-energy radiation to damage cancer cells. It may be combined with chemotherapy in selected situations, particularly when local control is important.

Targeted therapy

Targeted medicines work against specific characteristics of cancer cells. For advanced gastric cancer, testing may include biomarkers such as HER2, which can help determine whether HER2-directed treatment is appropriate.

More recent treatment approaches also consider CLDN18.2, particularly in some HER2-negative advanced cancers. NCI guidance updated in 2025 includes CLDN18.2-targeted therapy among treatment options for selected advanced cases.

Immunotherapy

Immunotherapy helps the immune system recognise and attack cancer cells. It may be considered for selected patients, depending on factors such as PD-L1 expression and mismatch repair or microsatellite instability status.

For advanced gastric adenocarcinoma, testing for HER2, PD-L1, and MSI or mismatch repair status can help guide treatment decisions.

Palliative and supportive care

Advanced cancer cannot always be removed completely. In such cases, treatment may focus on controlling cancer, slowing its progression and improving quality of life.

Supportive care can also help manage pain, nausea, nutritional problems, anaemia and other treatment-related or disease-related symptoms. Palliative care can be provided alongside cancer treatment and is not limited to the final stages of illness.

Can Stomach Cancer Be Prevented?

Not every case can be prevented, but certain steps may help lower risk:

• Get tested and treated for H. pylori when medically recommended.
• Avoid smoking and tobacco products.
• Limit heavily salted, smoked and poorly preserved foods.
• Include a variety of fruits and vegetables in the diet.
• Maintain a healthy weight and regular physical activity.
• Discuss a strong family history of stomach cancer with a doctor.
• Seek medical advice for persistent or unexplained digestive symptoms.

There is currently no universal screening programme for stomach cancer in many countries, including the United States. Screening may nevertheless be considered for people at particularly high inherited or familial risk.

When Should You See A Doctor?

Occasional indigestion or bloating is common and usually has a less serious cause. However, persistent symptoms should be evaluated, especially if they are accompanied by unexplained weight loss, repeated vomiting, difficulty swallowing, blood in vomit or black stools.

Early evaluation does not mean that cancer is likely. It simply helps identify the cause and ensures that potentially serious conditions are not overlooked.

Conclusion

Stomach cancer can be difficult to recognise early because its initial symptoms may resemble common digestive problems. Persistent symptoms, unexplained weight loss or signs of bleeding should therefore be evaluated rather than ignored. Diagnosis through endoscopy, biopsy and appropriate staging allows doctors to develop a treatment plan suited to the individual.

If you are looking for specialised cancer and gastrointestinal care, Regency Hospitals, one of the best hospital in Kanpur provides dedicated cancer and gastro care with multidisciplinary diagnostic, surgical and treatment services.

FAQs 

Is stomach cancer curable?

It can be curable, particularly when diagnosed at an early stage and the cancer can be completely removed. The outlook depends on factors including the cancer type, stage, location, overall health and response to treatment.

What are the most common stomach cancer symptoms?

Common symptoms include indigestion, upper abdominal discomfort, bloating, early fullness, nausea, vomiting, reduced appetite and unexplained weight loss. Difficulty swallowing and gastrointestinal bleeding can occur as well.

Is H. pylori infection linked to stomach cancer?

Yes. Long-term H. pylori infection can cause chronic inflammation and is an established risk factor for gastric cancer. Appropriate diagnosis and treatment of the infection may help reduce risk.

Does stomach cancer always cause pain?

No. Some people have no noticeable symptoms in the early stages. Pain can occur, but it is not necessary for stomach cancer to be present.

How is stomach cancer confirmed?

An upper endoscopy with a biopsy is generally central to confirming the diagnosis. Imaging and other tests are then used to determine the extent of the disease and guide treatment.

What tests help decide the treatment?

Apart from staging tests, doctors may examine the tumour for biomarkers such as HER2, PD-L1 and MSI or mismatch repair status. These results can help determine whether targeted therapy or immunotherapy may be useful.

What is the difference between stomach cancer and gastric cancer?

They refer to the same condition. “Gastric cancer” is the medical term commonly used for cancer that begins in the stomach.

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• Cancer: Symptoms, Causes, Types, Stages, Treatment & Prevention 
• Understanding Cancer: Types, Symptoms & Early Detection 
• 10 Commandments of Cancer Prevention – Regency Healthcare 
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