melanoma /mel′ənō″mə/ pl. melanomas, melanomata [Gk, melas + oma, tumor] , any of a group of malignant neoplasms that originate in the skin and that are composed of melanocytes. A melanocytic nevus may be acquired or congenital. The congenital melanocytic nevus is regarded as more likely to develop into a malignant melanoma, primarily because of its larger size. Smaller melanomas tend to develop from a pigmented nevus over several months or years. They may be sporadic and occur most commonly in fair-skinned people having light-colored eyes. A previous sunburn increases a person’s risk. Any black or brown spot having an irregular border; pigment appearing to radiate beyond that border; a red, black, and blue coloration observable on close examination; or a nodular surface is suggestive of melanoma and is usually excised for biopsy. Melanomas are most commonly located on the upper back and lower legs of fair-skinned individuals and on the palms of the hands and insoles of the feet of dark-skinned individuals. Melanomas may metastasize and are among the most malignant of all skin cancers. Prognosis depends on the kind of melanoma; its size, depth of invasion, and location; and the age and condition of the patient. Because of the occurrence of melanomas and melanocytic nevi in certain families, a familial atypical mole and melanoma syndrome has been designated. It is defined by the occurrence of melanoma in one or more first- or second-degree relatives, a large number of moles, and moles that demonstrate certain cellular features. Patients with the syndrome have a high lifetime risk of development of melanoma. Compare blue nevus. Kinds include benign juvenile melanoma, lentigo maligna melanoma, primary cutaneous melanoma, superficial spreading melanoma, amelanotic melanoma, nodular melanoma. See also Hutchinson’s freckle.
