Malignant melanoma is a neoplasm that arises from melanocytes. It's potentially the most lethal of the skin cancers. It's also relatively rare, accounting for only 1 % to 2% of all malignant tumors. Melanoma is slightly more common in women than in men and is unusual in children. Peak incidence occurs between ages 50 and 70, although the incidence in younger age groups is increasing.
Melanoma spreads through the lymphatic and vascular systems and metastasizes to the regional lymph nodes, skin, liver, lungs, and central nervous system. Its course is unpredictable and recurrence and metastases may not appear for more than 5 years after resection of the primary lesion. The prognosis varies with the tumor thickness. In most patients, superficial lesions are curable, whereas deeper lesions tend to metastasize.
Common sites for melanoma are the head and neck in men, the legs in women, and the backs of people exposed to excessive sunlight. Up to 70% of malignant melanomas arise from a preexisting nevus. It seldom appears in the congunctiva, choroid, pharynx, mouth, vagina, or anus.
The four types of melanomas are as follows:
Several factors may influence the development of melanoma:
Signs and Symptoms
Your doctor may have suspected melanoma after talking with you about your health and completing a physical examination. Or perhaps you noticed a new mole or a change in a mole you already had.
A skin biopsy is usually necessary to confirm a melanoma diagnosis. In this procedure, the mole is removed and checked under a microscope. A skin biopsy often requires a local anesthetic.
A patient with malignant melanoma always requires surgical resection to remove the tumor (a 3- to 5-cm margin is desired). The extent of resection depends on the size and location of the primary lesion. Closure of a wide resection may necessitate a skin graft. If so, plastic surgery techniques provide excellent cosmetic repair. Surgical treatment may also include regional lymphadenectomy.
Deep primary lesions may merit adjuvant chemotherapy. The most consistently used drugs have been dacarbazine and carmustine. After surgical removal of a mass, intra-arterial isolation perfusions are performed to prevent recurrence and metastatic spread.
Although still experimental, biotherapy, consisting of treatment with bacille Calmette-Guerin (BCG) vaccine, offers hope to patients with advanced melanoma. In theory, immunotherapy combats cancer by boosting the body's disease-fighting systems.
Chemotherapy is useful only in metastatic disease. Dacarbazine and the nitrosoureas have generated some response. Similarly, radiation therapy is usually reserved for metastatic disease. It doesn't prolong survival but may reduce tumor size and relieve pain.
Regardless of treatment, melanomas require close long-term follow-up care to detect metastases and recurrences. Statistics show that about 13% of recurrences develop more than 5 years after primary surgery.
Prevention is the best way to avoid this disease. Though malignant melanoma can develop anywhere on the body, and is not always caused by sun-damage to skin, the majority of new cases are caused by repetitive sun-exposure and chronic sun-damage. Minimizing sun exposure will significantly decrease your risk of getting melanoma. (Please refer to our page on minimizing sun exposure to learn exactly how to do this.) Avoiding sunburns and wearing sunscreen (SPF of 15 or better) on all exposed skin is important in preventing this disease. Keeping a good lookout for changing moles is the key to finding melanoma early.
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