Staging melanoma

The stage of a cancer is a term used to describe the size and depth of the melanoma, and whether it has spread. Knowing the stage of your cancer helps doctors decide on the best treatment for you.42

The TNM staging system

The staging system used for melanoma is the American Joint Committee on Cancer (AJCC) system. This is known as the TNM system.42

• T represents the thickness of the tumour in mm and whether it is ‘ulcerated’ (the skin is broken on the surface of the tumour).
• N stands for lymph nodes. It indicates whether the melanoma has spread to the lymph nodes and, if so, to how many.
• M stands for metastases. It indicates whether the melanoma has spread to other parts of the body (advanced or metastatic cancer). 

Measuring thickness

When melanomas are staged, doctors use a measurement to describe how thick (deep) the melanoma is. This is called the Breslow thickness (named after the doctor who introduced it). It measures how far the melanoma cells have grown down into the layers of skin. Most people have stage 1 melanomas, which are 1mm thick or less.42 

Number staging (0 – 4)

As well as the TNM and Breslow staging, doctors also use a number staging system. Melanomas are divided into four number stages. Below is a simple summary of the stages.42

Stage 0 melanoma

The cells are only present in the top layer of skin (the epidermis) and have not spread to the dermis. Stage 0 melanoma is also called melanoma in situ.42

Because the melanoma is only in the very top layer of the skin, people with melanoma in situ do not usually have any risk of the melanoma spreading to other parts of the body. 43

Stage 1 melanoma 42

Stage 1 melanomas are no more than 2mm thick and have not spread. They can be divided into:

Stage 1A: 

The melanoma is less than 1mm thick, without ulceration

Stage 1B:

The melanoma is less than 1mm thick, with ulceration

OR

The melanoma is between 1-2mm thick, without ulceration

Stage 2 melanoma 42

Stage 2 melanomas are usually thicker than stage 1 but have not spread. They can be divided into:

Stage 2A

The melanoma is between 1-2mm thick, with ulceration

OR

The melanoma is between 2-4mm thick, without ulceration

Stage 2B

The melanoma is between 2-4mm thick, with ulceration

OR

The melanoma is thicker than 4mm, without ulceration

Stage 2C

The melanoma is thicker than 4mm with ulceration

Stage 3 melanoma 42,44

Stage 3 melanomas have spread to the lymphatic vessels or lymph nodes closest to the melanoma, but not to anywhere else in the body. In stage 3, the thickness of the melanoma is not a factor, but the melanoma is usually thick.

Stage 3 melanoma is divided into stages 3A, 3B, 3C or 3D depending on factors such as:

• the number of lymph nodes involved
• whether the lymph nodes contain melanoma cells that can be seen by the naked eye or only under a microscope
• whether melanoma cells are found in the skin or lymphatic vessels near the melanoma

Stage 4 melanoma42

Stage 4 melanoma has spread to other organs such as the lungs, liver, bones or brain. This is called metastatic melanoma.

You may want to ask your doctor these questions about staging of melanoma:

• What stage is my melanoma? What does this mean?
• How will the stage of melanoma affect treatment options available to me?
• Does this mean the melanoma has spread?
• How can I prevent the melanoma from spreading?
• What steps can I take to reduce the risk of developing a new melanoma or other type of skin cancer?

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