Stages of Melanoma Skin Cancer

After someone is diagnosed with melanoma, doctors will try to figure out if it has spread, and if so, how far. This process is called staging.

The stage of a cancer describes how much cancer is in the body. It helps determine how serious the cancer is and how best to treat it. Doctors also use a cancer’s stage when talking about survival statistics.

How is the stage determined?

The staging system most often used for melanoma is the American Joint Committee on Cancer (AJCC) TNM system, which is based on 3 key pieces of information.

T describes the main (primary) tumor, including how deeply the cancer has grown into the skin and whether the cancer is ulcerated.

• Tumor thickness (Breslow measurement): Melanomas less than 1 millimeter (mm) thick have a very small chance of spreading. As the melanoma becomes thicker, it has a greater chance of spreading.
• Ulceration: This is a sore over the melanoma. Melanomas that are ulcerated tend to have a worse outlook.

N describes spread to nearby lymph nodes.

M describes spread (metastasis) to distant parts of the body. Melanoma can spread almost anywhere in the body, but the most common sites of spread are the lungs, liver, brain, bones, skin, and lymph nodes in other parts of the body.

Numbers or letters after T, N, and M provide more details about each of these factors. Higher numbers mean the cancer is more advanced.

Once a person’s T, N, and M categories have been determined, this information is combined in a process called stage grouping to assign an overall stage.

The earliest melanomas are stage 0 (melanoma in situ) and then range from stages I through IV. Some stages are split further, using capital letters (A, B, etc.). As a rule, the lower the number, the less the cancer has spread. And within a stage, an earlier letter means a lower stage.

Clinical stage vs. pathological stage

There are 2 main types of staging for melanoma.

• The clinical stage is based on the results of physical exams, biopsies, and any imaging tests that have been done. The clinical stage can be used to help determine if more tests are needed, to help plan treatment, and to give an idea of a person’s outlook.
• The pathological stage, also called the surgical stage, might be determined if surgery is done after the skin biopsy to remove more of the area around the skin tumor or check nearby lymph nodes for cancer.

Sometimes the pathological stage might be different from the clinical stage. For example, it might become clear during surgery that the cancer has grown farther than what could be seen on imaging tests.

To learn more about how cancer is staged, see Cancer Staging.

Stages of melanoma

Below is a simplified version of the clinical stages of melanoma in the most recent TNM system. If your cancer has been pathologically staged, it is best to talk to your doctor about your specific stage.

Melanoma staging can be very complex, so if you have any questions about the stage of your cancer or what it means, ask your doctor to explain it to you in a way you understand.