It is important for your doctors to know what kind of cancer you have. Different cancer types are generally determined by the part of the body the tumor is in and the type of cells that make up the tumor.

The most common sites where cancer develops include the skin, lungs, breasts, prostate, colon, and rectum.

The three main types of cells that cancers start in are as follows:

• Epithelial cells. Cancers that start in these cells are called carcinomas. About 80-90% of all cancer cases are carcinomas.
• The cells of the blood and lymphatic system. Cancers that develop in this type of cells are called leukemias and lymphomas. Leukemias and lymphomas make up about 7% of all cancer cases.
• Cells of connective tissue. Cancers that develop in these cells are called sarcomas. About 1% of all cancers are sarcomas.

Cancer can develop in other types of cells, but this happens only rarely.