Malignant Melanoma

A neoplasm that arises from melanocytes, malignant melanoma is relatively rare and accounts for only 1 % to 2% of all types of cancer. The three types of melanomas are superficial spreading melanoma, nodular malignant melanoma, and lentigo maligna melanoma.

Melanoma is slightly more common in women than in men and is rare in children. Peak incidence occurs between the ages of 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 (CNS). Its course is unpredictable, however, and recurrence and metastasis may occur more than 5 years after resection of the primary lesion.

The prognosis varies with tumor thickness. Generally, superficial lesions are curable, while deeper lesions tend to metastasize. The Breslow Level Method measures tumor depth nom the granular level of the epidermis to the deepest melanoma cello Melanoma lesions less than 0.76 mm deep have an excellent prognosis, while deeper lesions (more than 0.76 mm) are at risk for metastasis. The prognosis is better for a tumor on an extremity (which is drained by one lymphatic network) than for one on the head, neck, or trunk (drained by several networks).

Causes

No one knows why a cancer starts. Melanoma cancer may arise by itself or it may begin to grow out of an abnormal mole. Heredity may also play a role because some families have more of a melanoma risk than others. Fair skin people seem to be at greater risk for developing melanoma than darker skinned people. Excessive sun exposure, especially if burning occurs during childhood, may increase the risk of getting melanoma.

Among Western countries, the number of people who develop melanoma has been increasing over the years. In the United States, the number of new cases of this cancer has more than doubled in the past 20 years.

Most dermatologists believe that regular use of sunscreen decreases risk for the development of malignant melanoma.

Signs and symptoms

The first sign of melanoma is often a change in the size, shape, color, or feel of a mole on the skin. These changes can be remembered as "ABCD":

• Asymmetry - an odd shape, or one half is shaped differently from the other
• Border - ragged, notched, blurred, or irregular outline
• Color - different shades of black, brown, and tan in the same mole; there may also be patches of white, gray, red, pink, or blue in it
• Diameter - the mole grows larger; melanomas are usually larger than ¼ inch across

Diagnosis

A skin biopsy with histologic examination can distinguish malignant melanoma from a benign nevus, seborrheic keratosis, and pigmented basal cell epithelioma; it can also determine tumor thickness. Physical examination, paying particular attention to lymph nodes, can point to metastatic involvement.

Baseline laboratory studies include a complete blood count with differential, erythrocyte sedimentation rate, platelet count, liver function studies, and urinalysis. Depending on the depth of tumor invasion and metastasis, baseline diagnostic studies may also include a chest X-ray and computed tomography (CT) scan of the chest and abdomen. Signs of bone metastasis may call for a bone scan; CNS metastasis, a CT scan of the brain.

Treatment

A patient with malignant melanoma requires surgical resection to remove the tumor. The extent of resection depends on the size and location of the primary lesion. Closure of a wide resection may require a skin graft. Surgical treatment may also include regional lymphad enectomy.

Deep primary lesions may merit adjuvant chemotherapy and biotherapy to eliminate or reduce the number of tumor cells. Radiation therapy is usually reserved for metastatic disease; it doesn't prolong survival but may reduce tumor size and relieve pain.

Regardless of the treatment method, melanomas require close, long-term follow-up to detect metastasis and recurrences.

Alternative treatment

Though radiation therapy has a minimal role in the primary treatment of malignant melanoma, for patients who have metastatic disease, radiation may be helpful. This is true in patients who have developed tumor deposits in such areas as the brain or bone.

Prevention

Though it is difficult to prove that sunscreens statistically reduce the frequency of malignant melanoma at this time, most authorities recommend their use as protection from ultraviolet light (considered a major factor in the development of melanoma.) Avoidance of severe sunburns is recommended.