Abstract
A 14-year-old male grey wolf (Canis lupus) with a history of severe facial swelling was submitted for necropsy. Clinical and radiological examination demonstrated an expansile neoplastic mass in the nasal and frontal sinuses. On necropsy, an amorphous neoplastic mass and extensive necrosis were observed in the nasal turbinate. Microscopic examination revealed a tumour principally composed of obvious clear tumour cells characterised by small hyperchromatic nuclei and abundant clear cytoplasm. These clear cells were positive for mucin with PAS, PAS-D reaction, and alcian blue (pH 2.5) staining, but negative for PTAH staining. Immunohistochemically, some of tumour cells were strongly positive for mesenchymal cells (vimentin), whereas they were negative for myoepithelial antigen (alpha-SMA) and cytokeratin. Based on the histopathological and immunohistochemical features, the present case was diagnosed as high-grade clear cell variant mucoepidermoid carcinoma (MEC). This is the first description of clear cell variant MEC in a wolf.