Malignant melanoma is a serious type of skin cancer. It is one of the rarer types of skin cancer but causes the majority of skin cancer related deaths. Moles that are irregular in color or shape are suspicious of a malignant or a premalignant melanoma. Around 160,000 new cases of melanoma are diagnosed worldwide each year, and it is more frequent in males and caucasians. Melanoma is most common on the back in men and on legs in women (which are areas of intermittent sun exposure). It is more common in caucasian populations living in sunny climates than other groups. Malignant melanoma accounts for 75 percent of all deaths associated with skin cancer.

What causes malignant melanoma?

Malignant melanoma is caused by uncontrolled growth of the skin's pigment cells, which are called melanocytes. Epidemiologic studies suggest that exposure to ultraviolet radiation (UVA and UVB rays) is one of the major contributors to the development of melanoma. Use of tanning beds (with deeply penetrating UVA rays) has been linked to the development of skin cancers, including melanomas. UV radiation causes damage to the DNA of cells, which when unrepaired can create mutations in the cell's genes. When the cell divides, these mutations are passed on to the new generations of cells. If the mutations occur in certain genes, the rate of division in the mutation-bearing cells can become uncontrolled, leading to the formation of a tumor.

How is malignant melanoma diagnosed?

To detect melanomas (and increase survival rates), it is recommended to learn what they look like to be aware of moles and check for changes (shape, size, color, itching or bleeding) and to show any suspicious moles to a doctor with an interest and skills in skin malignancy.

A popular method for remembering the signs and symptoms of melanoma is the mnemonic "ABCD":

Asymmetrical skin lesion.
Border of the lesion is irregular.
Color: melanomas usually have multiple colors.
Diameter: moles greater than 6 mm are more likely to be melanomas than smaller moles.

Sometimes a skin lesion that is suspicious for melanoma may bleed, itch, or ulcerate, although this is a very late sign. A slow-healing lesion should be watched closely, as that may be a sign of melanoma.

Following a visual examination and a dermatoscopic exam, used routinely by one in 4 dermatologists in the United States, or an examination using other in vivo diagnostic tools, such as a confocal microscope, the doctor may biopsy the suspicious mole. If it is malignant, the mole and an area around may need wider excision by a surgeon, depending on the melanoma's size and severity.

What is the treatment for malignant melanoma?

Excisional skin biopsy is the management of choice; this is where the suspect lesion is totally removed with an adequate (but minimal, usually 1 or 2 mm) ellipse of surrounding skin and tissue. The preferred surgical margin for the initial biopsy should be narrow (1 mm) in order to prevent the disruption of the local lymphatic drainage. The biopsy will include the epidermal, dermal, and subcutaneous layers of the skin, enabling the pathologist to determine the depth of penetration of the melanoma by microscopic examination.

It is common for patients diagnosed with melanoma to have chest X-rays and and possibly an LDH test, and in some cases CT, MRI, PET and/or PET/CT scans. Sentinel lymph node biopsies and examination of the lymph nodes are also performed in some patients to assess the degree of possible spread to the lymph nodes. Melanomas which spread usually do so to the lymph nodes in the region of the tumor before spreading elsewhere.

Although controversial and without prolonging survival, "sentinel lymph node" biopsy is often performed, especially for T1b/T2+ tumors, mucosal tumors, ocular melanoma and tumors of the limbs. A process called lymphoscintigraphy is performed in which a radioactive tracer is injected at the tumor site in order to localize the "sentinel node(s)". Further precision is provided using a blue tracer dye and surgery is performed to biopsy the node(s).

High risk melanomas may require adjuvant treatment (oncologic treatment prior to surgery). Various chemotherapy agents are used, including dacarbazine (also termed DTIC), immunotherapy (with interleukin-2 (IL-2) or interferon (IFN)) as well as local perfusion are used by different centers. Radiation therapy is often used after surgical resection for patients with locally or regionally advanced melanoma or for patients with unresectable distant metastases.

What is the prognosis for a patient with malignant melanoma?

Certain types of melanoma have worse prognoses but this is explained by their thickness. Interestingly, less invasive melanomas even with lymph node metastases carry a better prognosis than deep melanomas without regional metastasis at time of staging. Local recurrences tend to behave similarly to a primary unless they are at the site of a wide local excision (as opposed to a staged excision or punch/shave excision) since these recurrences tend to indicate lymphatic invasion.

When melanomas have spread to the lymph nodes, one of the most important factors in determining the patient's prognosis is the number of nodes with malignancy. In this scenario, sentinel lymph node mapping is done to determine which nodes, if any, have malignancy.

Stage 0: Melanoma in Situ (Clark Level I), 99.9% Survival

Stage I/II: Invasive Melanoma, 85-95% Survival

Stage II: High Risk Melanoma, 40-85% Survival

Stage III: Regional Metastasis, 25-60% Survival

Stage IV: Distant Metastasis, 9-15% Survival