What is Melanoma?

Melanoma is a type of skin cancer, and arises in the melanocytes, which are the cells which give our skin pigment. Your biopsy report, which showed the diagnosis of melanoma, also describes a number of features of your particular tumor which are used to estimate prognosis as well as to make treatment decisions. The most important of these is the thickness (not the diameter) of the melanoma measured in millimeters, also known as the Breslow’s depth. Tumor thickness is generally grouped into three categories: thin (less than 1mm), intermediate (1-4 mm), and thick (greater than 4mm). The thicker the tumor, the greater is the potential to spread, or metastasize. Ulceration, in which the pathologist observes tissue breakdown on the surface of the tumor, suggests more aggressive behavior. The mitotic rate describes the number of dividing cells the pathologist sees within one square millimeter; this is often seenon the pathology reports as, for example, 3/mm2 , meaning 3 mitotic figures (dividing cells) in an areameasuring one square millimeter. The higher the number, potentially the more aggressive the tumor willbe. Lymphatic invasion, vascular invasion, and lymphovascular invasion are all terms describingwhether the pathologist identified tumor cells within the lymphatic vessels, blood vessels, or both in thebiopsy specimen. The margins, or edges or the biopsy specimen, are described as being negative (notumor cells at the edge of the specimen), or positive (in which tumor cells are seen at the edge of thebiopsy specimen). A positive margin implies there are remaining tumor cells in your incision site, whichrequires further surgery.


There are two main issues regarding surgical treatment of melanoma: (1) the margin, or amount of normal skin which needs to be removed around the melanoma, and (2) whether there is enough concernfor tumor spreading to the lymph nodes to perform a sentinel lymph node biopsy (SLNB).We have learned that if a melanoma is removed with a small amount of normal appearing skin around it,there is an increased chance that the melanoma could come back in the same area because of unseenmelanoma cells present outside the visible tumor; this is known as a local recurrence. A large number ofclinical trials have resulted in guidelines which are used by the surgeon. These can be summarized asfollows: for melanoma in situ (an early, noninvasive melanoma) a 5 mm margin is used. For melanomaless than 1mm in depth the recommended margin in 1 centimeter; while for a melanoma 1-2 mm in depththe recommended margin is between 1-2 centimeters. For melanomas greater than 2mm in depth a 2 cmmargin is recommended. There is some flexibility allowed depending on anatomic location and otherfactors; these will be discussed during your visit. In general an ellipse of skin is removed which canusually be closed with stitches; sometimes a skin graft may be necessary. Complications from thisoperation, also known as a wide local excision, can include bleeding, infection, poor wound healing,numbness or tingling around the incision. Melanoma has the potential to spread by either blood vessels or the lymphatic vessels (lymph nodes). Lymph nodes are part of your body’s immune system; when you experience “swollen glands” in your neck with a sore throat, you are feeling enlarged lymph nodes fighting the virus which is causing that sore throat. Lymph nodes are also involved with fighting tumors; the presence of tumor cells in lymph nodes indicates a more aggressive and serious stage of disease. Typically melanoma spreads to the lymph nodebasin closest to it; for example, either the armpit or groin area on the same side as the tumor; sometimesthere can be spread to more than one lymph node basin (which can contain multiple nodes). The deeperthe melanoma, the higher the risk for lymph node spread. Standard recommendations today (see NCCNguidelines) are to evaluate the regional nodes for melanomas between 1-4 mm and some thick melanomas(greater than 4 mm). In general, thin melanomas (less than 1 mm) do not require lymphatic evaluationbecause there is such a small chance of lymphatic spread. However, some thin melanomas exhibit “highrisk” features such as ulceration, an increased mitotic rate, or lymphatic or vascular invasion; these mightwarrant lymphatic evaluation.