Primary Adenosquamous Cell Carcinoma of the Ileum in a Dog

A 9-year-old male, castrated Chihuahua was examined because of a 7-day history of intermittent vomiting. A mass in the small intestine was identified on abdominal radiography and ultrasonography. Laparotomy revealed a mass lesion originating in the ileum, and surgical resection was performed. The mass was histologically diagnosed as adenosquamous cell carcinoma. Chemotherapy with carboplatin was initiated, but the dog was suspected to have experienced recurrence 13 months after surgery and died 3 months later. To our knowledge, this is the first case report to describe the clinical course of adenosquamous cell carcinoma in the small intestine of a dog.