The pathological characteristics of enzootic nasal adenocarcinoma in goats.

INTRODUCTION: Enzootic nasal adenocarcinoma (ENA) is a nasal cancer that occurs in goats and sheep infected by enzootic nasal tumour virus. Pathologic examinations are useful for distinguishing tumours from inflammatory hyperplasia. The aim of this study was to describe the pathological characteristics of ENA. MATERIAL AND METHODS: Caprine tumour samples were collected for pathological examination. The tissue sections were stained with haematoxylin-eosin and periodic acid-Schiff (PAS) and processed for immunohistochemical staining. Tumour samples were also processed for routine transmission electron microscopy (TEM). RESULTS: The histopathological structure of the tumours exhibited both papillary formations in the superficial regions and tubular or acinar formations in the deeper layers, representing distinct structural patterns within the same adenocarcinoma. The tumour cells were positive for PAS, and mitotic figures were rare. Low-differentiated cancer nests and epithelial-mesenchymal transition phenomena were observed. Immunohistochemical analysis showed that the tumour cells were strongly positive for pancytokeratin and cytokeratin (CK)18, moderately positive for CK7, and did not express olfactory marker protein. The Kiel 67 labelling index was approximately 23%. Retrovirus-like particles were distributed inside and outside of acinar tumour cells in TEM. CONCLUSION: The origin site of ENA is the epithelium of the nasal glandular tubules. This cancer is a low-grade adenocarcinoma with malignant potential. Cytokeratin 7 and CK18 can be considered immunophenotypes for identifying ENA tumour cells.