[Increased risk of developing a second primary cutaneous nevus-associated melanoma in patients previously diagnosed with the disease].

BACKGROUND Patients diagnosed with primary cutaneous melanoma have a greater lifetime risk of developing further melanomas. Most of these melanomas appear to arise de novo, but a proportion of them develop in pre-existing melanocytic nevi. OBJECTIVE To determine risk factors associated with the development of a second cutaneous melanoma arising on a nevus in patients diagnosed with cutaneous melanoma. PATIENTS AND METHODS A series of 981 patients diagnosed with cutaneous melanoma was selected; 47 of them had been diagnosed with a second melanoma. These 47 patients were classified into 2 groups according to whether or not there was histological evidence that the melanoma was associated with a nevus. RESULTS Age at diagnosis less than 40 years, tumor location on the trunk, and superficial spreading subtype were independent risk factors for the appearance of a primary melanoma on a nevus. The only factor associated with the appearance of a second nevus-associated melanoma was that the first melanoma was also associated with a nevus (odds ratio, 9.51; 95% confidence interval 1.6-56.56; P=.042). CONCLUSIONS Nevus-associated melanomas develop mainly in young patients, on the trunk, and are of the superficial spreading subtype. A history of primary cutaneous melanoma arising on a nevus is associated with a 9-fold increase in the risk of developing a second nevus-associated melanoma. These findings highlight the need for careful follow-up of all melanocytic lesions in patients who have had a primary nevus-associated melanoma.