All cancers have a scale they follow based on how far the cancer has advanced. For melanoma skin cancer, the stage is based on several factors, including the depth of the cancer, if it’s ulcerating, how many cells are growing out of control called mitoses, and if the lymph nodes are involved. The best case scenario is a very thin melanoma that has no ulceration, no mitoses, and has not spread to the lymph nodes. That’s considered stage zero and doctors might refer to it as “in situ.” The number of the stage changes as you go deeper. T1 is one millimeter deep, T2 is two to three, T3 is three to four millimeters, and T4 is greater than four millimeters deep. The chances of the cancer spreading to other parts of your body called metastatic cancer increases the deeper the cancer is.