melanoma
(mel‵ă-nō'mă 
)
[ melano- + -oma ]
A malignant tumor of darkly pigmented cells (melanocytes) that often arises in a brown or black mole. The tumor can spread aggressively throughout the body, e.g., to the brain and other internal organs.
SEE: illus..
Incidence: The incidence of the disease is rising rapidly in the U.S., esp. among people over 60. In 2023, the American Cancer Society estimated that approx. 98,000 people would be diagnosed with melanoma and that nearly 8,000 would die of the disease.
Causes: Excessive exposure to ultraviolet light, esp. sunlight, contributes to the development of melanoma, as does a family history of the disease. It is more common in fair-skinned than dark-skinned people and more common in people who have many moles on the skin than in those who have few. Total body skin examinations should be performed periodically on high-risk patients. On average, consistent screening identifies melanomas at an earlier stage (when they are thinner, or localized, rather than after they have spread) than those found on routine examination.
Prevention: People spending considerable time outside should wear protective clothing to shield against ultraviolet radiation and use sunscreens (at least SPF15) on exposed skin.
Common melanoma sites are the back, shoulders, head and neck (for men), and the legs and back (for women). A skin biopsy and histologic examination can distinguish malignant melanoma from a benign nevus, seborrheic keratosis, or pigmented basal cell epithelioma; it also determines tumor thickness and tumor stage. Staging is based on the TNM system and Clark’s levels system, which classifies tumor progression according to skin layer penetration. Once diagnosed, patients need physical, psychological, and social assessment and care. Treatment options should be explained.
Treatment: Melanomas are treated with surgery to remove the tumor and surrounding tissue, and with immunotherapy, radiation therapy, and targeted drug therapies.
Impact on Health: The likelihood of long-term survival depends on the depth of the lesion (thicker lesions are more hazardous), whether it is ulcerated, the histological type (nodular and acral lentiginous melanomas are more dangerous than superficial spreading or lentigo malignant melanomas), the patient's age (older patients do more poorly), and gender (men tend to have a worse prognosis than women). The likelihood of metastatic spread of melanoma is greatest in the first 5 years after diagnosis. For advanced melanomas, regular imaging studies (ultrasound, CT, or PET scans) are recommended every 6 to 12 months during this period. Less frequent follow-up is recommended thereafter.
SEE: ABCD; skin cancer.
Patient Care: After surgery, dressings are inspected for drainage and signs of infection, and the patient is taught about prevention and signs to report. When therapy fails, the patient and family will need referrals for palliative (hospice) care and may also require social services and spiritual care.
desmoplastic m.A rare melanoma in which the typical melanotic pigmentation may be absent. It often occurs on the head or neck. Microscopically, the tumor cells are spindle-shaped. Local recurrences after surgical excision are common, as are metastases, esp. to the lungs.
in situ m.A superficial melanoma that has not yet invaded deep layers of the skin or spread to local or distant tissues.
The lesion should be removed by an experienced surgeon.
Patients diagnosed with melanoma in situ need careful follow-up examinations in case the tumor recurs, spreads, or is associated with other skin cancers.
small-diameter m.A melanoma measuring less than 6 mm in diameter.
thin mA melanoma that measures less than 1 mm in thickness. Thin melanomas have a better prognosis than thicker ones.