Ocular and perineal squamous cell carcinomas in a Holstein Friesian cow.

Background: Squamous cell carcinoma (SCC) in domestic cattle is an economically significant malignant neoplasm and has been documented primarily in ocular and periocular tissues, vulva, and perineum. SCCs are often slow-growing and locally invasive, but metastasis is uncommon. Increased risk of developing SCC has been predominantly associated with high levels of sunlight exposure and hypopigmentation (skin and conjunctiva). This manuscript reports a case of ocular and perineal SCC in a Holstein Friesian cow with maxillary sinusitis secondary to tumor invasion. Case Description: An approximately 17-year-old Holstein Friesian cow was presented with a swollen, closed left eye and slow-growing perineal masses. The left eye was exenterated after showing poor response to anti-inflammatory and antimicrobial therapies, and the largest perineal mass was excised. Twelve months later, the cow developed purulent nasal discharge and dyspnea. The animal was euthanized for postmortem investigation due to health deterioration, advanced age, and suspected tumor metastasis. Conclusion: Ocular and perineal SCCs were diagnosed on biopsy and confirmed with immunohistochemistry. Postmortem gross and histological evaluations confirmed SCC invasion in the left maxillary sinus, with a secondary