Carcinoma in situ describes a cancer in the very earliest stage. At this point, the cancer is quite small and has not invaded the tissues around it.

What is going on in the body?

Cancer develops in several stages. A cancer begins when a single cell becomes cancerous. This happens when the central control of the cell is damaged. The cell begins to grow and multiply out of control. When enough of these cells are produced, they form a tumor. The tumor will eventually grow large enough to press on the tissue around it. The tumor will also invade and destroy the tissue around it. When a tumor has formed but has not begun to invade tissue, it is said to be "in situ," which means in place. Some cancers may stay in this stage for a long time. Most cancers, however, do not stay in situ for long and begin to spread. Cancers found in situ are the easiest to cure because they have not spread.

What are the causes and risks of the disease?

The risks for developing a particular type of carcinoma in situ are the same as the risks for developing that type of cancer.