Nasal fibroma associated with bovine papillomavirus-2 in a Japanese Black steer

Abstract

A 15‑month‑old Japanese Black steer developed bilateral nasal masses at the nose-ring insertion site. Masses were excised surgically and showed no invasion of the underlying nasal or incisive bones. The animal recovered uneventfully and was slaughtered at 29 months of age without carcass defects. The lesions were elastic with reddish‑pink to red nodules. Histologically, they were composed of fibroblast‑like neoplastic cells embedded in abundant collagenous stroma, and fibroma was diagnosed. BPV‑2 L1 gene was amplified by PCR. Tumor cells showed positive immunohistochemical staining for BPV E2 protein and positive in situ hybridization signals for BPV E5 mRNA, indicating active BPV-2 involvement. This is the first report of a BPV‑2–associated fibroma arising at a bovine nose‑ring insertion site.