Pigmented dermal duct tumour (Winkelmann-McLeod type poroma) in a ring-tailed lemur (Lemur catta)

A pigmented dermal duct tumour was diagnosed in a 12-year-old female ring-tailed lemur ( Lemur catta ) kept in a zoo. The tumour developed on the ventral surface of the left fourth digit and appeared as a black, solid, ulcerated nodule. Histologically, it was a well-demarcated, non-encapsulated dermal proliferation of basaloid neoplastic epithelial cells forming solid nests with scattered small duct-like lumina. Scattered melanocytes and abundant melanin pigment were present within the tumour. There was no continuity between the tumour and the epidermis. Immunohistochemically, the basaloid neoplastic epithelial cells were positive for pan-cytokeratin and p63 but negative for cytokeratin 19, α-smooth muscle actin, vimentin, Sox10, DOG1, S100, PNL2 and Melan-A. Neoplastic luminal cells were positive for pan-cytokeratin and cytokeratin 19, but negative for p63. Based on the morphological and immunohistochemical findings, the tumour was diagnosed as a pigmented dermal duct tumour that corresponds to one of the subtypes of benign human poroid neoplasms. To our knowledge, this is the first report of this neoplasm in a ring-tailed lemur.