Pinkus tumor may originate from intraepidermal eccrine ducts and proliferate in the dermis.

To clarify the histopathogenesis of Pinkus tumor (fibroepithelial basal cell carcinoma, FEBCC), we have studied cytokeratin (CK) expression in FEBCC using ten different anti-keratin antibodies against CK 1, 7, 8, 10, 14, 15, 16, 17, 18 and 19. Tumor nests consisted of two epithelial components: duct-like structures and basaloid cells of anastomosing strands. In duct-like structure, CK 1, 10, 14, 16, 17 and 19 were detected. CK expression of duct-like structure showed the hyperproliferative state of eccrine intraepidermal ducts. In basaloid cells of anastomosing strands, CK 14 and 17 were detectable. These results suggested that duct-like structure originates from the intraepidermal duct and proliferates to spread in the dermis.