Malignant Melanoma

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:

• Superficial spreading melanoma, the most common type, usually develops between ages 40 and 50.
• Nodular melanoma usually develops between ages 40 and 50. It grows vertically, invades the dermis, and metastasizes early.
• Acrallentiginous melanoma is the most common melanoma among Hispanics, Asians, and Blacks. It occurs on the palms and soles and in sublingual locations.
• Lentigo maligna melanoma is relatively rare. This is the most benign, slowest growing, and least aggressive of the four types. It most commonly occurs in areas heavily exposed to the sun. It arises from a lentigo maligna, on an exposed skin surface, and usually occurs between ages 60 and 70.

Causes

Several factors may influence the development of melanoma:

• Excessive exposure to sunlight. Melanoma occurs most commonly in persons in sunny, warm areas and often develops on body parts that are exposed to the sun.
• Skin type. Most people who develop melanoma have blond or red hair, fair skin, and blue eyes; are prone to sunburn; and are of Celtic or Scandinavian ancestry. Melanoma is rare among Blacks; when it does develop, it usually arises in lightly pigmented areas (the palms, plantar surface of the feet, or mucous membranes).
• Hormonal factors. Pregnancy may increase the risk of melanoma and exacerbate growth.
• Family history. Melanoma occurs slightly more often within families.
• Past history of melanoma. A person who has had one melanoma is at greater risk of developing a second.

Signs and Symptoms

• The color of the tumours vary from brown or black to blue or orange.
• The tumour may resemble a 'blood blister' under a nail.
• The tumours are characterised by having ragged edges and uneven colors.
• The mole may itch.
• Off-shots, sores, crusts, and reddening may be seen in the area surrounding the mole.
• Moles can be found anywhere on the body, but are typically located on the back, the shoulders, or the back of the legs.

Diagnostic tests 

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.

Treatment

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

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.