Primary nasal histiocytic sarcoma of macrophage-myeloid cell type in a cat.

A 16-year-old neutered male Burmese cat was presented with a locally invasive nasal mass. The cytological and histological findings on incisional biopsy of this mass were suggestive of histiocytic sarcoma. Tumour cells expressed CD18, major histocompatibility complex class II, lysozyme and alpha-naphthyl acetate esterase; and lacked expression of CD3, CD79a, CD1a, CD1b, calprotectin, CD11c and E-cadherin. These findings are consistent with a myeloid-macrophage lineage. Metastasis to the bone marrow was present on necropsy examination. Histiocytic sarcoma should be considered in cats presented with primary round cell neoplasia of the nasal cavity.