Malignant melanoma is by far the most serious of the three most common types of skin cancer,
but it is fortunately the least common. Melanoma usually appears as a changing mole (nevus) or
as a new mole that has developed suddenly. Melanomas are typically pigmented (having a dark color)
but can rarely be flesh-colored (known as amelanotic melanoma).
Skin lesions that are suspicious
for melanoma typically meet one or more of the "ABCDE" criteria:
- A-Asymmetry, having a different shape on one half as compared to the other half.
- B-Border irregularity, such as a jagged border.
- C-Color variations, including multiple colors or especially the color black.
- D-Diameter, usually greater than 6 mm.
- E-Evolution, or change in a mole
Melanoma can occur anywhere on the skin surface without a strong predilection for sun-exposed areas.
Although there is a strong link between a person's risk of melanoma and a history of excessive sun
exposure during childhood, there are probably many other factors involved.
Genetic predisposition is known to play a role in the development of melanoma as individuals with a close relative
who has had melanoma are at increased risk.
People with numerous moles, especially when those moles are atypical (known as dysplastic nevi or dysplastic moles),
also have a greater risk of developing melanoma.
Other factors that lead to the development of melanoma and the reasons for the marked increase in incidence in recent decades have yet to be fully defined. This is one focus of current research.
Melanomas are derived from melanocytes, which are the pigment cells normally found in the outermost layer of the skin (epidermis). As a melanoma grows prior to its detection, the cells invade deeper and deeper into the skin where they may encounter blood and lymphatic vessels, thereby greatly increasing the chances of spread to other parts of the body (i.e., lymph nodes). Melanoma in situ is the best case scenario in which the melanoma cells are still in their "site of origin" and have not begun to invade the deeper layer of skin (dermis). Lentigo maligna is a term used to describe a melanoma in situ occurring on severely sun-damaged skin, most commonly the face.
Although there are a number of factors that affect prognosis in a patient with melanoma, the most important factor is the determination of the Breslow depth, which is a quantitative measurement of the depth to which the cancerous cells have reached in the skin. This measurement is made in millimeters by the dermatopathologist once the lesion has been removed. If the pathology results reveal that the melanoma cells have not grown very deeply into the skin, then the risk of spread to other bodily sites is low. In contrast, melanomas that have invaded more deeply into the skin are associated with a greater risk for metastasis. There are more than 8,000 deaths due to melanoma every year in the United States. The key to saving lives is catching melanoma early in its course before it grows deeply into the skin and metastasizes. When caught early and properly treated, melanoma has an excellent cure rate and long-term survival rate exceeding 90%.
Treatment of melanoma must adhere to the latest standards of care in order to maximize the chances of a long-term cure. Central to definitive management of melanoma is wide local excision, which is the surgical removal of the biopsy site and a rim of normal-appearing skin around it. For patients with thinner, lower risk melanomas, lymph node removal is not necessary and does not improve the long-term outcome. However, patients with higher risk melanomas may benefit by having a sentinel lymph node biopsy, a procedure in which the lymph node most likely to have metastatic disease is identified and removed, or by having a full lymph node dissection. Consideration for adjuvant therapy under the direction of a medical oncologist, which may include radiation or interferon treatment, is necessary only for patients with higher-risk melanomas. After a patient has undergone definitive treatment, he or she is at increased risk for the development of another, separate melanoma, so long-term ultraviolet protection and regular skin examinations are important.
For patients who have been recently diagnosed with malignant melanoma, we have the following step-by-step recommendations made in keeping with the latest guidelines of care published by the
American Academy of Dermatology:
- Wide local excision with, or most often without, lymph node removal.
- General physical examination by a primary care physician.
- Blood testing and x-rays considered optional unless general physical exam and review of systems uncover an abnormality that makes them necessary.
- Consideration for adjuvant therapy necessary only for patients with higher-risk melanomas.
- Avoid exposure to ultraviolet light as much as possible.
- Complete skin examination by a dermatologist at least every six to twelve months for two years, then every year thereafter. Perform a monthly self-examination of your skin, and get an immediate appointment if there are any suspicious changes.
- All first-degree relatives (mother, father, siblings, and children) should be instructed that they are at increased risk for the development of melanoma.
