Stomach cancer, also known as gastric cancer, starts in the stomach. The stomach is a sac-like organ that aids in holding food and digests it through secretion of gastric juice. The medical term used to refer to the stomach area is the abdomen, and it includes the appendix, small intestine, colon and other organs that surround it. (1)
The stomach is divided into the following parts:
- Proximal stomach: Consists of the cardia, fundus, and corpus (body)
- Distal stomach: Consists of the antrum and pylorus that acts as a valve that controls emptying of the stomach contents into the small intestine. (2)
The stomach is also divided into different layers which are:
- Mucosa: the innermost layer that helps in the formation of stomach acid and digestive enzymes. It is where most cancers begin in the stomach.
- Submucosa: a supporting layer of the stomach.
- Muscularis: this is a thick layer of muscle that mixes the stomach contents.
- Subserosa and serosa: lastly, these are the outermost layers of the skin that wraps the stomach.
These layers play a role in determining the extent of cancer and one’s prognosis. Cancer usually grows after a very extended period. This is because they start in different sections of the stomach. Stomach cancer can metastasize in a variety of ways and can grow through the walls and invade other nearby tissues. The cancerous cells can also attack the lymph vessels and the lymph nodes which are structures that help in fighting infections.
What Are The Types Of Stomach Cancer?
Stomach cancers are grouped according to the part of the stomach infected, and the following are the types:
Adenocarcinoma: It is the most common type of cancer because it constitutes to about 90% to 95% of cancers of the stomach. Doctors commonly refer to this type of cancer when they mention stomach cancer. They often develop from the cells that make up the mucosa (the innermost layer of the stomach). (3)
Lymphoma: These are cancers that occur in the lymphatic system tissues that are present in the stomach walls. However, it constitutes to a tiny percentage of cancers of the stomach.
Gastrointestinal Stromal Tumor (GIST): It a rare type of tumor that starts in the interstitial cells of Cajal which are early forms of cells present in the stomach walls. Nevertheless, gastrointestinal stromal tumor (GIST) can occur in any part of the digestive tract, but most of them are present in the stomach.
Carcinoid Tumor: These are tumors that start in the cells that make hormones in the stomach. Additionally, these tumors rarely metastasize to other organs, and they are the rare types.
Other unique and rare types of stomach cancers include:
- small cell carcinoma,
- squamous cell carcinoma