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What are the stages of Melanoma?

When a melanoma has been diagnosed, the pathology report provides information to determine the "stage” of the disease.

The prognosis of melanoma and the treatment options available depend on the stage at which the cancer is diagnosed.

One of the most common areas of confusion is the difference between the levels of melanoma and the staging of melanoma. The level of melanoma relates to the depth of the melanoma in the skin and the staging of melanoma refers to how limited or advanced the melanoma is at the time of diagnosis.

The stages of melanoma are determined by reviewing different factors including:

Breslow Depth

Tumour depth or thickness is measured in millimetres by a pathologist using a microscope. This is referred to as the ‘Breslow Depth’. The thicker the tumour, the greater the chance it might have metastasised (spread) to regional lymph nodes or distant sites. Thinner melanomas have a better prognosis.

Less than 1mm:Thin melanoma
1-4mm:Intermediate melanoma
Greater than 4mm:Thick melanoma

The tumour depth was traditionally described using a ‘Clark level’ to indicate the number of layers of skin penetrated by the melanoma. The Clark level is a number from I-V with V being the deepest penetration of the skin.  The usage of Clark levels has been replaced by the updated melanoma staging system which uses more reliably predictive features such as ulceration, mitotic count and Breslow depth.  Clark levels are discussed further in the Glossary.

Tumour Ulceration

Ulceration of a skin tumour means that the epidermis (or top layer of the skin) that covers the melanoma is not intact. Ulceration may not be seen with the naked eye. Ulcerated melanomas pose a greater risk for metastatic progression.

Number of metastatic lymph nodes involved

If the melanoma has spread to the lymph nodes the risk of spread to other parts of the body is higher. The greater the number of lymph nodes containing melanoma, the less favourable the prognosis.

A sentinel node biopsy is a technique used to determine whether melanoma cells have spread to lymph nodes at the time of diagnosis of the skin primary lesion. The procedure involves the injection of a radioactive tracer by a radiologist (in the radiology department), to show where the site and lymph node where the lymph fluid from the skin at the primary melanoma will flow. Afterwards, at the same time as the extra surgery for the primary melanoma a blue dye is injected around the site of the primary lesion. Using the guide from the radiologist a surgeon looks for the first lymph node to take up the dye. The lymph node is removed and sent to be examined by a histopathologist to determine if the node tests positive for melanoma. The procedure is considered when the Breslow thickness of the melanoma is more than 0.8mm.

Patients may develop lumps in the lymph node regions such as the neck, armpit and groin. This is lymph node metastasis.

Distant metastasis

Melanoma that has spread in the blood steam may grow in any site in the body.

Stages of Melanoma:

Stage 0

In Stage 0 melanoma, the malignant cells are confined to the upper layer of the skin (epidermis or Level I). This means that the cancer cells are only in the outer layer of the skin (epidermis) and have not grown any deeper. The term for this is in situ, (which means ‘in place’ in Latin) or Level 1. There is no evidence the cancer has spread to the lymph nodes or distant sites.

Stage I

Stage I melanoma is defined as a melanoma that is up to 2mm thick. There are two subclasses of Stage I: 1A (less than 0.8mm); 1B ( 0.8 -1mm or any melanoma less than 1mm with ulceration and melanoma 1-2mm without ulceration). There is no evidence the cancer has spread to lymph nodes or distant sites (metastasis).

Stage II

Stage II melanoma. There are three subclasses of Stage II: IIA (1-2mm with ulceration and 2-4mm without ulceration); IIB (2-4mm with ulceration and more than 4mm without ulceration); IIC (more than 4mm with ulceration). There is no evidence the cancer has spread to the lymph nodes or distant sites (metastasis).

Stage III

Stage III melanoma is defined by the presence of lymph node involvement combined with the thickness and ulceration in the primary skin melanoma. There are four subclasses of Stage III Melanoma: IIIA, IIIB, IIIC, IIID. The subclasses relate to the size and number of glands that contain the melanoma cells. There is no evidence the cancer has spread to distant sites (metastasis).

Stage IV

Stage IV melanoma is defined when the melanoma has spread beyond the original site and regional lymph nodes to more distant areas of the body. The blood level of LDH (serum lactate dehydrogenase) in the patient may or may not be elevated. The significance of this is that it provides biochemical evidence of metastatic spread. The most common sites of metastasis are to vital organs (lungs, abdominal organs, brain, and bone), soft tissues (skin, subcutaneous tissues) and distant lymph nodes (lymph nodes beyond the primary tumour region).

 

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