Case Report: Nasal acinic cell carcinoma in a cat: clinicopathological and immunohistochemical characterization of a rare neoplasm

Abstract

Acinic cell carcinoma (ACC) is a malignant epithelial neoplasm characterized by serous acinar differentiation and is most described in the salivary glands of humans and domestic animals. In animals, ACC is rare and its occurrence in the nasal cavity of cats is exceptionally uncommon. This case describes the clinical presentation, gross pathological findings, histological features and immunohistochemical profile of a nasal acinic cell carcinoma in a 14-year-old domestic shorthair cat. The animal showed chronic unilateral nasal discharge and epiphora. Bacteriological culture of nasal secretions yielded Pasteurella spp. and despite antimicrobial therapy the clinical condition worsened. Post-mortem examination revealed a whitish mass destroying the nasal turbinates extending to the frontal sinus. Histologically, the tumor exhibited solid, microcystic and follicular growth patterns, with moderate cellular atypia and cytoplasmic PAS-positive granules. Immunohistochemical analysis demonstrated diffuse positivity for pan-cytokeratin, with differential expressions of cytokeratin 8 and S-100 protein depending on the growth pattern, while α-smooth muscle actin was negative in neoplastic cells. These findings are consistent with biphasic acinic cell carcinoma showing mixed acinar and ductal differentiation. There are scant histological and immunohistochemistry complete descriptions of nasal acinic cell carcinoma in the feline species. This case states the importance of considering this rare entity in the differential diagnosis of chronic unilateral nasal disease, particularly, in older cats.