ABSTRACT
Objective:To investigate clinical and histopathological features of congenital melanocytic nevi (CMN) complicated by proliferative nodules (PN) .Methods:Ten patients with clinically and pathologically confirmed CMN complicated by PN were collected from Department of Dermatology, the Fourth Military Medical University from 2015 to 2019, and their clinical and pathological data were analyzed retrospectively.Results:The 10 patients were aged from 2 to 45 years, with an average age of 15 years. Nine patients developed PN in infancy, and 1 in adulthood. The skin lesions were located on the extremities in 4 cases, on the head and face in 3 cases, and on the trunk in 2 cases, and the trunk and extremities were both involved in 1 case. Skin lesions clinically manifested as 1 or more nodules arising in black patches or plaques. Six patients presented with multiple PN, 4 with solitary PN, with the diameter of a single nodule being 0.2-1.5 cm, and only 1 case presented with ulcers. Histopathological examination showed mature melanocytes in the PN, with few mitotic figures, no obvious cytological atypia, and no necrosis. Immunohistochemical study showed that nevus cells diffusely expressed Melan-A, but did not express or partially expressed HMB45, and the Ki67 proliferation index was below 5%.Conclusion:CMN complicated by PN can occur on the extremities, head, face, and trunk, clinically manifesting as solitary or multiple nodules on pre-existing CMN; histopathologically, mature melanocytes can be observed in PN, immunohistochemical staining for HMB45 and Ki67 can facilitate the diagnosis, and its prognosis needs long-term follow-up.