Stages of Skin Cancer
Stage 0 In stage 0 skin cancer, cancer is found only in the epidermis (the topmost layer of the skin), which is the layer of cells in which the cancer began. Stage 0 cancer is also called carcinoma in situ.
Stage I In stage I skin cancer, the tumor is 2 centimeters or smaller.
Stage II In stage II skin cancer, the tumor is larger than 2 centimeters.
Stage III In stage III skin cancer, cancer has spread below the skin to cartilage, muscle or bone and/or to nearby lymph nodes, but not to other parts of the body.
Stage IV In stage IV skin cancer, the cancer has spread to other parts of the body.

Source: National Cancer Institute, accessed on October 9, 2009.