# The pathological characteristics of enzootic nasal adenocarcinoma in goats

## TL;DR

This study describes the pathological features of a nasal cancer in goats caused by a virus, helping to distinguish it from other nasal conditions.

## Contribution

The study identifies specific histopathological and immunohistochemical markers for diagnosing enzootic nasal adenocarcinoma in goats.

## Key findings

- ENA tumors show distinct structural patterns with papillary and tubular formations.
- Tumor cells are positive for CK18 and CK7, but not for olfactory marker protein.
- Retrovirus-like particles were observed in tumor cells using electron microscopy.

## Abstract

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.

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).

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.

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.