[The number and distribution of nevus cell nevi in patients with malignant melanoma].

Total-body cutaneous examination of 211 patients with malignant melanoma (MM) and 157 controls showed that patients with MM had significantly more nevi. Among MM patients, men had more nevi on the trunk than women, and women had more nevi on the lower extremities than men. Men had an MM distribution that was similar to their nevus distribution. Women, however, had proportionately more MM on the legs and fewer MM on the neck. The "nevus density," defined as the number of nevi per unit surface area of skin, was higher in male MM patients. The nevus density was highest on the head and neck, and lower on the lower extremities and anterior trunk. Patients with nodular melanoma had more nevi than those with superficial spreading melanoma. MM patients with a family history of many nevi had more nevi than those without such a history. Patients with a family history of MM did not show an increased number of nevi, but they had larger numbers of suggestive nevi removed than those without a family history of MM. We believe that many of these observations are consistent with the view that MM is caused by a genetic predisposition to an overactive melanocytic system in combination with an external stimulant, such as UV radiation.