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

Abstract

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.