Natural History of Atypical and Equivocal Melanocytic Lesions in Children: An Observational Study of 19 Cases Maria A. Pizzichetta, M.D.,* Renato Talamini, Sc.D.,* Ignazio Stanganelli, M.D.,† and Hans Peter Soyer, M.D., F.A.C.D.‡ *Centro di Riferimento Oncologico, National Cancer Institute, Aviano, Italy, †Skin Cancer Unit, Istituto Tumori Romagna, Meldola, Italy, ‡Dermatology Research Centre, School of Medicine, University of Queensland, Translation Research Institute, Princess Alexandra Hospital, Brisbane, Queensland, Australia Abstract: Digital dermoscopy follow-up helps to identify patterns of change typical of common atypical nevi and early melanoma and improves the follow-up of patients with atypical nevi. We report the morphologic changes observed over time in 19 atypical or equivocal acquired melano- cytic nevi that underwent dermoscopic follow-up. Two observers retro- spectively examined digitalized dermoscopic images of 19 atypical melanocytic nevi from 15 children and young adults (median age 12 years, range 3–26 years). The images were assessed for global dermoscopic patterns at baseline and after a median 25-month (range 6–138 mos) follow- up. Ten (52.6%) nevi changed and nine (47.4%) retained a stable dermo- scopic pattern. Of the 10 changing lesions, 2 of 4 homogeneous nevi evolved into a reticular pattern and 2 into a mixed pattern; 1 of 2 nevi with a mixed pattern evolved into a homogeneous nevus and 1 into a regressing nevus; 1 of 2 nevi with “other” patterns, such as negative pigment network and peppering throughout the lesion, evolved into a mixed nevus and 1 into a regressing nevus; 1 globular nevus evolved into a mixed pattern; and 1 starburst nevus evolved into a homogeneous nevus. The most striking results of our study were that atypical nevi can evolve into common nevi or they can regress, as documented by long-term dermoscopic follow-up. In children and young adults, dermoscopic follow-up of atypical nevi might be a valid alternative to surgical excision and enables us to achieve new insights into the natural history of these nevi. Clark nevi (atypical melanocytic nevi) are acquired melanocytic lesions named after Wallace H. Clark, who first drew attention to this particular type of nevus by studying numerous melanocytic nevi in patients with concomitant melanomas (1). These nevi, originally named B-K moles, have also been called Address correspondence to Maria A. Pizzichetta, M.D., Divi- sion of Medical Oncology, C-Preventive Oncology, Centro di Riferimento Oncologico, ICCRS, Via Franco Gallini 2, 33081 Aviano, Italy, or e-mail: pizzichetta@cro.it. DOI: 10.1111/pde.12259 © 2014 Wiley Periodicals, Inc. 331 Pediatric Dermatology Vol. 31 No. 3 331–336, 2014