Stages of melanoma explained

Melanoma is staged mainly by determining the thickness of the tumor and whether the cancer has spread to the lymph nodes or other parts of the body. Determining the thickness of the tumor is done using a newer staging system called Breslow’s thickness. Breslow’s thickness is a measure of how deeply the tumor has penetrated the skin. The tumor thickness is usually measured from the top of the tumor to the deepest tumor cells.

The most important factors in staging melanoma include: the thickness of the tumor (Breslow’s thickness), whether the tumor is ulcerated (has broken through the skin), whether the tumor has spread to the lymph nodes and if the lymph nodes are conjoined, and whether the tumor has spread to other areas of the body. 

Breslow’s thickness is measured in millimeters and is the distance between the top layer of the skin (epidermis) and the deepest part of tumor underneath the skin. Thinner melanoma tumors have a better survival rate, while thicker tumors are linked to a lower survival rate. This is why Breslow’s thickness is one of the most important factors in determining the prognosis of the disease.

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Breslow’s thickness:

·         Non-invasive, in situ melanoma is confined to the epidermis (outer layer of skin)

·         Thin melanoma tumors are less than 1.0 mm

·         Intermediate melanoma tumors are between 1.0 and 4.0 mm

·         Thick melanoma tumors are larger than 4.0 mm

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Stages of melanoma:

Stage 0: Melanoma in situ

Abnormal melanocytes are present in the epidermis (outer layer of skin). These can potentially become cancerous and spread locally to tissue close by.

Stage I: Early stage melanoma. Tumor has penetrated the skin, but not by much.

In stage I melanoma, cancer has developed. This stage is broken down into two stages: IA and IB. Stage IA is when the tumor is no more than 1mm thick and there is no ulceration. Stage IB is when the tumor is either no more than 1mm thick and has ulceration or is more than 1mm thick but not more than 2mm thick and has no ulceration.

Stage II: Still early stage melanoma. Tumor has penetrated the skin more deeply.

Stage II melanoma is still considered and early stage of melanoma. This stage is broken down into three stages: IIA, IIB, IIC. Stage IIA is when the tumor is either more than 1mm thick but no more than 2mm thick and has ulceration, or is more than 2mm thick but no more than 4 mm thick and has no ulceration. Stage IIB is when the tumor is either more than 2mm thick but no more than 4mm thick and has ulceration, or is more than 4mm thick and has no ulceration.

Stage III: Locally advanced melanoma; tumor has spread beyond original tumor site and reached nearby lymph nodes.

Once the melanoma tumor has advanced to stage III, the Breslow’s thickness is no longer relevant and therefore no longer included in staging. The presence of ulceration becomes the most important factor in determining the progression of the disease. In stage III, the tumor has either spread to the lymph nodes or to the skin between the primary tumor and the nearby lymph nodes.

In stage III melanoma, the tumor may be any thickness, with or without ulceration. During this stage, one or more of the following occur: the cancer has spread to one or more lymph nodes, the lymph nodes are conjoined, the cancer is in a lymph vessel between the primary tumor and lymph nodes close by (more than 2cm away), or small tumors are present on or under the skin, but not more than 2cm away from the primary tumor.

Stage IV: Advanced melanoma.

In Stage IV, the melanoma tumor has spread beyond the original tumor site and has reached distant lymph nodes or other organs (usually lungs, liver, brain, bone, and gastrointestinal tract).