Incidence of new and changed nevi and melanomas detected using baseline images and dermoscopy in patients at high risk for melanoma.

OBJECTIVE To determine the incidence of new, changed, and regressed nevi and melanomas in a cohort of patients at high risk for melanoma using baseline total body photography and dermatoscopy. DESIGN Cohort study of patients at high risk for melanoma who underwent baseline cutaneous photography between January 1, 1992, and December 31, 1997, and had at least 1 follow-up visit by December 31, 1998. SETTING Private practice rooms of 1 dermatologist in conjunction with a public hospital-based, multidisciplinary melanoma clinic in Victoria, Australia. PATIENTS A total of 309 patients who had at least 1 of the following risk factors for melanoma: personal history, family history, 100 or more nevi, or 4 or more dysplastic nevi. MAIN OUTCOME MEASURES Number of new, changed, and regressed nevi and melanomas detected and excised during the study interval. RESULTS The incidence of new, changed, and regressed nevi decreased with increasing age (P<.001), whereas the incidence of melanomas increased (P = .05). The number of dysplastic nevi at baseline was positively associated with the incidence of changed nevi (P<.001) and melanomas (P = .03). The use of baseline photography and dermatoscopy was associated with low biopsy rates and early detection of melanomas. The development of melanoma in association with a preexisting nevus was not directly correlated with a change in a preexisting lesion monitored by baseline photography. CONCLUSIONS Nevi are dynamic, and only a small percentage of all new and changed melanocytic lesions are melanomas. Patients younger than 50 years had a lower incidence of melanomas and a higher rate of new, changed, and regressed nevi when compared with patients older than 50 years. A new or changed pigmented lesion is more likely to be a melanoma in patients older than 50 years.