The stages of basal cell carcinoma are labeled zero through four and generally track the size and depth of the carcinoma, according to Cancer Treatment Centers of America. The higher the stage, the greater likelihood of the carcinoma spreading.
A number of features indicate the carcinoma is at a greater risk of spreading or recurring, explains Cancer Treatment Centers of America. These include a carcinoma greater than 2 millimeters in thickness; invasion into lower layers of skin or tiny nerves in the skin; and location on a hair-bearing lip or ear.
In stage zero, cancer cells are confined to the upper layer of the skin and have not spread deeper to the dermis, notes Cancer Treatment Centers of America. In stage one, the cancer is less than 2 centimeters across, has not spread to nearby lymph nodes or organs and has one or fewer high-risk features. A stage two carcinoma has grown larger than 2 centimeters but still not spread. A tumor with two or more high-risk features is also considered stage two. In stage three, the cancer has spread into facial bones or one nearby lymph node but not other organs. In stage four, the cancer has spread to one or more lymph nodes that are larger than 3 centimeters, and possibly to bones or other organs.