How is melanoma skin cancer staged?
The stage of a melanoma is a description of how widespread it is. 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), often followed by letters. 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. The stage is based mainly on 3 key pieces of information:
- How far the main tumor has grown within the skin and other factors (see below).
- Whether the cancer has spread to nearby lymph nodes.
- Whether the cancer has metastasized (spread) to distant organs.
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 have a very small chance of spreading. Thicker melanomas have a greater chance of spreading.
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 outlook.
Last Medical Review: 02/19/2014
Last Revised: 09/16/2014