Malignant epithelial tumors associated with <i>Felis catus </i>papilloma virus type 3 and type 4 infections at distinct anatomical sites in a domestic cat

A 12-year-8-month-old neutered male cat presented with multiple nail bed masses and an ulcerative lip lesion. PCR identified Felis catus papillomavirus type 3 (FcaPV3) in the nail masses and type 4 (FcaPV4) in the lip lesion. Histopathology revealed basosquamous cell carcinoma (BSCC) in the digits and Bowenoid in situ carcinoma (BISC) in the lip. Immunohistochemistry showed that tumor cells in both BSCC and BISC were positive for p16 and p63 and weakly positive for pRb; p53 was negative in BSCC but weakly positive in BISC. In situ hybridization confirmed FcaPV3 and FcaPV4 E6 genes in digital and lip tumors, respectively. Over 6 months, viral sequencing showed 23 nucleotide changes in FcaPV3, suggesting viral evolution. This is the first report of distinct malignant epithelial tumors independently induced by FcaPV3 and FcaPV4 in a cat.