How is melanoma skin cancer staged?

The stage of a melanoma is a description of how widespread the cancer is. This includes how thick it is and whether it has spread to the lymph nodes or any other organs. The tests described in the “How is melanoma found?” section are used to help decide the stage of the melanoma. The stage is very important because it affects the treatment and the outlook (prognosis) for recovery.

Stages are labeled using 0 and the Roman numerals I through IV (1-4). As a rule, the lower the number, the less the cancer has spread. A higher number, such as stage IV (4), means a more advanced cancer.

There are really 2 types of staging for melanoma. The clinical stage is based on what is found in the physical exam, skin biopsy, x-rays, CT scans, and so on. The pathological stage uses all of this information plus what is found during any biopsies of lymph nodes or other organs. So the clinical stage (which is done first) may be lower than the pathologic stage, which is found after the biopsy.

After looking at your test results, the doctor will tell you the stage of your cancer. Be sure to ask your doctor to explain your stage in a way you understand. This will help you decide on the best treatment for you.

Important factors for early-stage melanomas

For melanomas that have not spread, certain factors affect a person’s outlook and are therefore part of the staging.

The thickness of the melanoma is measured from the skin biopsy sample. The thinner the melanoma, the better the outlook. For the most part, melanomas less than about ¹/₂₅ of an inch thick (about the size of a period or a comma) have a very small chance of spreading. Thicker melanomas have a greater chance of spreading. The thickness of the melanoma is called the Breslow measurement.

Another important aspect for tumors is the mitotic rate. To measure this, the doctor counts the number of cells that are in the process of dividing in a certain amount of melanoma tissue. A higher mitotic rate (having more cells that are dividing) means that the cancer is more likely to grow and spread.

Ulceration is a breakdown of the skin over the melanoma. Melanomas that are ulcerated tend to have a worse prognosis.