In situ squamous cell carcinoma of the gingiva and nictitating membrane associated with Felis catus papillomavirus type 3 in a cat.

Oral squamous cell carcinomas (OSCCs) are common cancers of cats. While papillomaviruses (PVs) are an important cause of human OSCCs, there is currently little evidence that PVs cause squamous cell carcinomas (SCCs) of the mouth or other mucosal surfaces in cats. In the present cat, in situ carcinomas developed on the gingiva and nictitating membrane. Neoplastic cells within both cancers contained prominent PV-induced cellular changes consistent with those caused by Felis catus PV3 (FcaPV3), and FcaPV3 DNA was amplified from both cancers. Neoplasms also contained intense nuclear and cytoplasmic p16 ^CDKN2A protein (p16) immunolabeling, suggesting PV-induced degradation of retinoblastoma protein. The molecular and histological features strongly suggested the cancers were caused by FcaPV3 infection. This is the first report of an association between PV infection and the development of an in situ carcinoma of the mucosa of cats. The identification of these lesions suggests that PVs might cause a proportion of OSCCs, and SCCs from other mucosal surfaces, in cats.