Stages of melanoma

Overview of melanoma cancer stages 0 – IV

Stage 0 melanoma (in situ)

Another term for Stage 0 melanoma is in situ, which means “in place” in Latin. In Stage 0 melanoma, the malignant tumour is confined to the upper layer of the skin (epidermis). This means the cancer cells are only in the outer layer of the skin and have not grown into the second layer of skin, called the dermis.

Stage 0 melanoma is not considered as invasive melanoma; and there is no evidence the cancer has spread. Stage 0 is local melanoma, meaning it has not spread beyond the primary tumour.

There are no subgroups for Stage 0 melanoma. In the TNM system, it’s described as TisN0M0

Risk: Patients with Stage 0 melanoma are considered at very low risk for local recurrence or for regional and distant metastases. 

Treatment: The standard treatment for Stage 0 melanoma (in situ) is surgery. 

Stage I Melanoma (localised tumour)

In Stage I melanoma, the cancer cells are in both the first and second layers of the skin—the epidermis and the dermis but has not spread any further. A melanoma tumour is considered Stage I if it is up to 2 mm thick, and it may or may not have ulceration. It can also be referred to as a local melanoma, meaning it has not spread beyond the primary tumour, but it is considered as an invasive melanoma, as it has spread to an additional layer of the skin.

There are two subgroups of Stage I melanoma: IA and IB which are defined by two primary characteristics: tumour thickness and ulceration. Tumour thickness (also called Breslow Depth) is how deeply the tumour has penetrated the skin. Ulceration is when the epidermis (or top layer of skin) that covers a portion of the primary melanoma is not intact. Ulceration can only be seen under a microscope, not by the naked eye.

Stage IA (1A)

• Tumours that are less than 0.8 mm without ulceration (T1aN0M0)

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Stage IB (1B)

• Tumours that are less than 0.8 mm with ulceration (T1bN0M0), OR
• Tumours that are greater than 0.8 mm and up to 2.0 mm without ulceration (T2aN0M0)

Risk: Patients with Stage I melanoma are considered low risk for local recurrence or for regional and distant metastases.

Treatment: The standard treatment for Stage I melanoma is surgery, called wide local excision. The purpose of the surgery is to remove any cancer remaining after the biopsy. Your doctor may also perform a sentinel lymph node biopsy based on the risk of the tumour spreading. 

Stage II melanoma (localised tumour)

In Stage II melanoma, the cancer cells are in both the first layer of skin (epidermis) and the second layer of skin (dermis) and has more high risk features. These features can be either due to depth of tumour or presence of ulceration, but there is no evidence the cancer has spread to lymph nodes or distant sites (metastasis). At this stage, the melanoma is still described as a local melanoma.

There are three subgroups of Stage II melanoma: IIA, IIB, and IIC which are defined by the Tumour thickness (also called Breslow Depth), which is how deeply the tumour has penetrated the skin; and Ulceration which describes when the epidermis (or top layer of skin) that covers a portion of the primary melanoma is not intact. Ulceration can only be seen under a microscope, not by the naked eye.

Stage IIA (2A)

• The tumour is 1.01 – 2.0 mm thick, with ulceration (T2bN0M0), OR
• The tumour is 2.01 – 4.0 mm thick, without ulceration (T3aN0M0)

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Stage IIB (2B)

• The tumour is 2.01 – 4.0 mm thick, with ulceration (T3bN0M0), OR
• The tumour is greater than 4.0 mm thick, without ulceration (T4aN0M0)

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Stage IIC (2c)

The tumour is greater than 4.0 mm thick, with ulceration (T4bN0M0)

Risk: With treatment, Stage II melanoma is considered intermediate to high risk for local recurrence or for regional and distant metastases.

Treatment: Can include surgery and sentinel lymph node biopsy (SLNB). If the lymph node biopsy is positive, then targeted therapy and/or immunotherapy may be considered as part of a clinical trial. This is considered a space where future adjuvant therapy may be likely to improve current recurrence and survival rates.

Stage III melanoma (regional spread)

Stage III melanoma describes tumours that have spread to nearby lymph nodes, or have spread from the primary tumour but haven’t yet reached the lymph node (called an in transit or satellite metastasis). There is no evidence of distant metastasis. Stage III melanoma is also described as a regional melanoma, meaning it has spread beyond the primary tumour as far as to the closest lymph nodes, but not as far as distant sites.

There are four subgroups of Stage III melanoma: IIIA, IIIB, IIIC, IIID which are defined by four characteristics: Primary tumour depth and ulceration; the number of lymph nodes to which it has spread; whether the tumour spread to the lymph node can be felt during a physical exam or seen on imaging tests; and how far the involved lymph nodes are from the primary tumour. Essentially these subgroups reflect the extent and degree of spread and growth in the lymph nodes.

Stage IIIA (3A)

• Tumours that are less than 2mm thick with or without ulceration (T1 or T2a), AND
• Up to 3 lymph nodes are involved but cannot be felt or seen, only visualised under a microscope (N1a or N2a)
• It has not spread to distant parts of the body (M0)

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Stage IIIB (3B)

• Either the primary tumour cannot be found (T0), or the tumour is less than 4mm thick with or without ulceration (T1, T2 or T3a) AND
• The tumour has spread to only one lymph node (N1a or N1b) OR
• The tumour has spread from the primary tumour but haven’t yet reached the lymph node (called an in transit or satellite metastasis) (N1c) OR
• The tumour has spread to 2 or 3 nearby lymph nodes (N2a or N2b)
• It has not spread to distant parts of the body (M0)

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Stage IIIC (3C)

• The primary tumour cannot be found (T0) ,OR the primary tumour can be any size with or without ulceration (T1, T2, T3 or T4), AND  
• The tumour has spread to 1 or more lymph nodes (N2b or N3b), OR
• The tumour has spread to lymph nodes that are clustered together (N3b or N3c) OR
• The tumour has spread from the primary tumour but haven’t yet reached the lymph node (called an in transit or satellite metastasis) (N2c or N3c), AND
• It has not spread to distant parts of the body (M0)

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Stage IIID (3D)

• The primary tumour is thicker than 4mm and is ulcerated (T4b), AND
• The tumour has spread to 4 or more lymph nodes (N3a or N3b), OR
• The tumour has spread to lymph nodes that are clustered together (N3b), OR
• The tumour has spread from the primary tumour to nearby skin and lymph channels (called an in transit or satellite metastasis) and has also reached 2 or more lymph nodes or to lymph nodes that are clustered together (N3c), AND
• It has not spread to distant parts of the body (M0)

Stage IV melanoma (metastasis beyond regional lymph nodes)

In Stage IV melanoma, the cancer has spread beyond the original tumour site and regional lymph nodes to more distant areas of the body. The most common sites of metastasis are distant skin and lymph nodes, then lungs, liver, brain, bone, and/or intestines. The level of serum lactate dehydrogenase (LDH) in the blood may or may not be elevated. The level of LDH is an important sign, as it usually indicates overall tumour burden and possibly how aggressive the tumour is—in other words, it usually indicates the amount of cancer in the body. Other terms used to describe stage IV are Advanced Melanoma or Metastatic Melanoma.

• The tumour can be any thickness or may not be detected (any T)
• The cancer may or may not have spread to nearby lymph nodes (any N)
• The cancer has spread to distant lymph nodes or to organs in the body like lungs, liver or brain (M1)
• Important distinctions within Stage IV: Location of different metastases, number and size of tumours, and LDH level