The staging system used for melanoma is the American Joint Committee on Cancer (AJCC) system. It uses the TNM system.
T stands for tumour. This is the thickness (depth) of the melanoma (using Breslow thickness). It also describes whether the melanoma is ulcerated. A melanoma is ulcerated if the layer of skin covering the melanoma cannot be clearly seen.
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 (secondary or metastatic cancer).
The AJCC system groups melanomas into an overall number stage between 1 and 4:
Stage 1 melanoma
Stage 1 melanomas are no more than 2mm thick and have not spread beyond the skin. Stage 1 melanoma can be divided into:
- Stage 1A – The melanoma is 1mm thick or less, without ulceration, and it has a mitotic rate of less than 1/mm2
- Stage 1B – The melanoma is 1mm thick or less. It also has either ulceration or a mitotic rate of at least 1/mm2. OR the melanoma is between 1.01mm and 2mm thick, but doesn’t have ulceration.
Mitotic rate describes the number of cells that are in the process of dividing in a certain amount of melanoma tissue. A higher mitotic rate means that the cancer has a greater risk of spreading.
Stage 2 melanoma
Stage 2 melanomas have not spread to the lymph nodes or anywhere else in the body. Stage 2 melanoma can be divided into:
- Stage 2A – The melanoma is between 1.01mm and 2mm thick, with ulceration. OR it is between 2.01mm and 4mm thick, without ulceration.
- Stage 2B – The melanoma is between 2.01mm and 4mm thick, with ulceration. OR it is thicker than 4mm, without ulceration.
- Stage 2C – The melanoma is thicker than 4mm with ulceration.
Stage 3 melanoma
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 or 3C, 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 melanoma
Stage 4 melanoma has spread to distant areas of skin or distant lymph nodes. Or it has spread to other organs such as the lungs, liver or brain. This is called advanced or metastatic melanoma.
The way cancers are staged is complicated. If you have any questions about the stage of your melanoma, ask your doctor.