Feline oral in situ carcinoma associated with papillomavirus infection: A case series of 7 cats.

Cutaneous lesions due to papillomavirus (PV) infection are well described in cats. However, there are few reports of similar lesions in the oral cavity. In this case series, 7 cats with in situ carcinomas of the oral mucosa are reported. Lesions appeared histologically like cutaneous Bowenoid in situ carcinomas, and PV-induced cell changes were visible within lesions from 6 cats. A PV etiology was further supported by intense p16CDKN2A protein immunolabeling within all lesions. Five lesions contained Felis catus papillomavirus (FcaPV) type 3 DNA, while 2 contained FcaPV1 DNA. Cats had clinical signs of drooling and oral pain for over 6 months prior to diagnosis, and the dorsal surface of the tongue was most often affected. Four cats had multiple oral lesions, and 2 cats had oral and skin lesions. Of the 6 cats for which clinical outcome was known, 3 are still alive at least 6 months after diagnosis, 2 died of unrelated causes 7 and 14 months after diagnosis, and 1 cat was euthanatized due to oral pain 18 months after diagnosis. Results suggest PV-associated oral in situ carcinoma is a specific disease entity of cats. Lesions are slowly progressive with pain management allowing long survival times. No cases were known to progress to invasive squamous cell carcinoma, and feline oral squamous cell carcinomas appear to infrequently develop as a progression from these lesions. Due to the marked difference in biological behavior, diagnosticians should differentiate PV-associated oral in situ carcinomas and oral squamous cell carcinomas in cats.