To investigate pathological characteristics and differential diagnosis of desmoplastic melanocytic nevus.

Four cases of desmoplastic melanocytic nevus were analyzed based on the clinical manifestations and histological, immunohistochemical and fluorescence in situ hybridization (FISH) features.

Of the 4 cases, 2 were male and 2 were female. Their age ranged from 19 to 30 years with the average age being 26.5 years. The skin lesions were located on the extremities in 3 cases, on the vulva in 1 case. Histologically, the lesions were bilaterally symmetrical intradermal nevus. Nevus cells appeared epithelioid and/or fusiform, some were clustered or scattered in the proliferative fibrous tissue. None of lymphocyte aggregation, necrosis or ulceration was observed. Immunohistochemical examination showed positive staining for S100 and Melan A in 3 cases, positive staining for P16 in 2 cases, Ki-67-labeling index less than 5% in all the 4 cases, and negative staining for factor XIII (FXIII) and CD34 in 2 cases. FISH assay showed no copy-number variations in gene loci 6p25 (RREB1) , 6q23 (MYB) , 6p11.1-q11.1 (Cep6) and 11q13 (CCND1) in desmoplastic melanocytic nevus.

Desmoplastic melanocytic nevus is a kind of histologically unique, benign melanocytic nevus, and immunohistochemical staining for Ki-67, S-100, Melan A and FⅩⅢand FISH assay on melanoma can be helpful for the differential diagnosis between cutaneous fibrous histiocytoma and melanoma.

Nevus, pigmented; Pathologic processes; Skin manifestations; Immunohistochemistry; Desmoplastic melanocytic nevi; FISH