Stomach cancer, also called gastric cancer, is a cancer that starts in the stomach. Stomach (gastric) cancers tend to develop slowly over many years. Before a true cancer develops, pre-cancerous changes often occur in the inner lining (mucosa) of the stomach.1 Stomach cancers also include cancer of the gastroesophageal junction (also known as the GEJ), where the esophagus meets the stomach.1 Stomach cancers can spread (metastasize) in different ways. Metastatic gastric (stomach or GEJ) cancer is cancer that began in the stomach or GEJ, but has spread to other parts of the body. They can grow through the wall of the stomach and invade nearby organs. They can also spread to the lymph vessels and nearby lymph nodes.1
Adenocarcinoma About 90% to 95% of cancers of the stomach are adenocarcinomas-arises from inner most lining of stomach- mucosa.1
Lymphoma arises from lymphoid tissue in stomach wall.1
Gastrointestinal stromal tumor (GIST) These are rare tumors that start in very early forms of cells in the wall of the stomach called interstitial cells of Cajal.1
Carcinoid tumors These are tumors that start in hormone-making cells of the stomach. Most of these tumors do not spread to other organs. About 3% of stomach cancers are carcinoid tumors.1
Other Cancers Other types of cancer, such as squamous cell carcinoma, small cell carcinoma, and leiomyosarcoma, can also start in the stomach, but these cancers are very rare.1
TNM : (T-Extension of tumor through stomach wall, N- Lymph node invasion, M- Metastasis)
Figure: Layers of stomach wall
Figure: Tumor extent through stomach wall
Recent studies indicate a role of HER2 (Human epidermal growth factor receptor 2) in the development of numerous types of human cancer. About 1 out of 5 of gastric cancers has too much of a growth-promoting protein called HER2/neu (or just HER2) on the surface of the cancer cell.1
1. Immunohistochemistry (IHC) test: In this test, special antibodies that stick to the HER2/neu protein are applied to the sample, which cause cells to change color if many copies are present. This color change can be seen under a microscope. The test results are reported as 0, 1+, 2+, or 3+.
2. Fluorescent in situ hybridization (FISH) test: This test uses fluorescent pieces of DNA that specifically stick to copies of the HER2/neu gene in cells, which can then be counted under a special microscope.
Trastuzumab anti HER2 antibody is considered as first line therapy in combination with chemotherapy for HER2 /neu overexpressing adenocarcinoma