Abstract: 【Abstract】 Objective To investigate clinical and histopathological characteristics of nevoid melanoma. Methods A retrospective analysis was carried out on clinical and histopathological data collected from 3 patients with nevoid melanoma diagnosed in Department of Dermatology, Xijing Hospital from 2000 to 2020. Results Among the 3 patients with nevoid melanoma, 2 were females and 1 was male. Skin lesions initially manifested as black macules and papules. After surgical resection, 2 patients developed new nodular lesions or recurrent skin lesions which enlarged into plaques. Histopathological examination showed proliferation of epithelioid melanocytes in the epidermis and dermis, with cytological atypia and some deeply stained nuclei. Immunohistochemical study revealed positive staining for Melan-A and S100 in tumor cells in the skin lesions, diffusely positive staining for HMB45 in dermal tumor cells, locally negative staining for HMB45 in the deep dermis, increased Ki67 proliferation index, and active expression of cyclin D1. Conclusion Nevoid melanoma is easy to be misdiagnosed as pigmented nevi or seborrheic keratosis; when recurrence or metastasis occurs in patients with histologically diagnosed pigmented nevi, attention should be paid to the possibility of nevoid melanoma.

Key words: Nevi and melanomas, Skin manifestations, Pathologic processes, Recurrence, Neoplasm metastasis, Nevoid melanoma