Usually we realize that someone has a melanoma because a mole has been removed or biopsied. This is usually done because the appearance of the mole is worrisome, or has been changing. When a mole is biopsied, it is sent to a pathologist. He can tell by the microscopic appearance that it is a melanoma.
The other information that the pathologist gives us is information about the thickness of the melanoma. This tells us how deeply into the skin the melanoma has penetrated. We want to know this because it is the most important indicator of the prognosis of the melanoma.
The thickness is described in two different ways:
The first way tells us through which layers of the skin the melanoma has penetrated. When the skin is viewed under a microscope there are several distinct layers, each with a different appearance. The pathologist assigns a "Clarke's Level" between one and five. This is always written with Roman Numerals. Level I is the least deep, just penetrating the outer epidermis of the skin. Level V is the deepest, down into the fat beneath the skin. The Clarke's Level is different than the "stage" of the melanoma, which is also written in Roman Numerals.
This system describes the actual thickness of the melanoma in millimeters. This is also used because the skin has different thickness on different parts of the body. The skin on the back is very thick; but the skin on the face is very thin. We usually divide patients into four groups based on thickness:
- less than 0.76mm (about 1/32 of an inch)
- 0.76-1.5 mm (1/32 to 1/16 of an inch)
- 1.5-4mm (1/16 to 1/6 of an inch)
- >4mm (over 1/6 of an inch)
The other piece of information that we need to determine treatment and prognosis of melanomas is the status of the lymph nodes adjacent to the melanoma. On some areas of the body, it is easy to tell which lymph nodes would be the significant ones: for example, for a melanoma on the arm the significant nodes would be in the armpit, for the leg the significant nodes would be in the groin.
It is more difficult to predict the nodes that drain melanomas on the back, belly, chest or head and neck. Sentinel node mapping is used to help us determine which nodes need to be biopsied in these patients.
Staging of Melanoma
To determine the "stage" of the melanoma, we need to put together the information about the depth of invasion, lymph node status, and information on any spread elsewhere in the body. The stage is referred to as Stage I through Stage IV. For more information on staging, one source is the Melanoma Patient's Information Page.
Treatment of Melanoma
Treatment consists of surgical removal of the melanoma, sentinel node biopsy and mapping, possibly complete lymph node removal, and possible adjuvant chemotherapy.