- Development of stomach cancer
Stomach 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. These early changes rarely cause symptoms and therefore often go undetected.
Cancers starting in different sections of the stomach may cause different symptoms and tend to have different outcomes. The cancer’s location can also affect the treatment options. For example, cancers that start at the GE junction are staged and treated the same as cancers of the esophagus.
Types of stomach cancers
Most (about 90% to 95%) cancers of the stomach are adenocarcinomas. A stomach cancer or gastric cancer almost always is an adenocarcinoma. These cancers develop from the cells that form the innermost lining of the stomach (the mucosa).
These are cancers of the immune system tissue that are sometimes found in the wall of the stomach. The treatment and outlook depend on the type of lymphoma.
Gastrointestinal stromal tumor (GIST)
These rare tumors start in cells in the wall of the stomach called interstitial cells of Cajal. Some of these tumors are non-cancerous (benign); others are cancerous. Although GISTs can be found anywhere in the digestive tract, most are found in the stomach.
These tumors start in hormone-making cells of the stomach. Most of these tumors do not spread to other organs
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.
Staging of Stomach or Gastric Cancer
If cancer cells are found in the tissue sample, the next step is to Stage the cancer, or find out the extent of the disease.
The clinical stages of stomach cancer are:
- Stage 0. Limited to the inner lining of the stomach.
- Stage I- Penetration to the second or third layers of the stomach (Stage 1A) or to the second layer and nearby lymph nodes (Stage 1B).
- Stage II- Penetration to the second layer and more distant lymph nodes, or the third layer and only nearby lymph nodes, or all four layers but not the lymph nodes.
- Stage III- Penetration to the third layer and more distant lymph nodes, or penetration to the fourth layer and either nearby tissues or nearby or more distant lymph nodes
- Stage IV- Cancer has spread to nearby tissues and more distant lymph nodes or has metastasized to other organs