Signs and symptoms
Stomach cancer is often either asymptomatic (producing no noticeable symptoms) or it may cause only nonspecific symptoms (which may also be present in other related or unrelated disorders) in its early stages. By the time symptoms are recognized, the cancer has often reached an advanced stage (see below) and may have metastasized (spread to other, perhaps distant, parts of the body), which is one of the main reasons for its relatively poor prognosis. Stomach cancer can cause the following signs and symptoms: Unexplained nausea, vomiting, diarrhoea and constipation. Patients also can experience unexplained weight loss.Early cancers may be associated with indigestion or a burning sensation (heartburn). However, fewer than one in every 50 people referred for endoscopy due to indigestion has cancer. Abdominal discomfort and loss of appetite, especially for meat, can occur.Gastric cancers that have enlarged and invaded normal tissue can cause weakness, fatigue, bloating of the stomach after meals, abdominal pain in the upper abdomen, nausea and occasional vomiting. Further enlargement may cause weight loss or bleeding with vomiting blood or having blood in the stool, the latter apparent as black discolouration (melena) and sometimes leading to anemia. Dysphagia suggests a tumour in the cardia or extension of the gastric tumour into the esophagus.These can be symptoms of other problems such as a stomach virus, gastric ulcer, or tropical sprue. Risk factors
Gastric cancer can occur as a result of many factors. It occurs twice as commonly in males as females. Estrogen may protect women against the development of this form of cancer.
A very small percentage of diffuse-type gastric cancers (see Histopathology below) arise from an inherited abnormal CDH1 gene. Genetic testing and treatment options are available for families at risk. Other
Other risk factors include diabetes, pernicious anemia, chronic atrophic gastritis, Menetriers disease (hyperplastic, hypersecretory gastropathy), and intestinal metaplasia.In addition, Foxp3 polymorphism (rs3761548) might contribute to gastric cancer development through influencing Treg cell activity. Diagnosis
To find the cause of symptoms, the doctor asks about the patients medical history, does a physical examination, and may order laboratory studies. The patient may also have one or all of these exams:

Gastroscopic exam is the diagnostic method of choice. This involves insertion of a fibre optic camera into the stomach to visualise it. Upper GI series (may be called barium roentgenogram)
Computed tomography or CT scanning of the abdomen may reveal gastric cancer. It is more useful to determine invasion into adjacent tissues or the presence of spread to local lymph nodes. Wall thickening of more than 1 cm that is focal, eccentric, and enhancing favours malignancy.In 2013, Chinese and Israeli scientists reported a successful pilot study of a breathalyzer-style breath test intended to diagnose stomach cancer by analyzing exhaled chemicals without the need for an intrusive endoscopy. A larger-scale clinical trial of this technology was completed in 2014.Abnormal tissue seen in a gastroscope examination is biopsied by the surgeon or gastroenterologist. This tissue is then sent to a pathologist for histological examination under a microscope to check for the presence of cancerous cells.