Tubulopapillary mammary carcinoma in a sloth bear (Melursus ursinus): Clinical presentation, diagnosis, and surgical outcome

Abstract

Mammary tumours are well-documented in domestic animals but rarely reported in wildlife, particularly in ursids. In domestic dogs, mammary neoplasms are common and serve as valuable comparative models for human breast cancer. In sloth bears (Melursus ursinus), neoplasms including cholangiocarcinoma and extrahepatic biliary carcinoma have been reported; however, to the authors’ knowledge, this is the first documented case of a mammary tumour in this species. A 24-year-old rescued female sloth bear presented with a progressively enlarging mass in the left pectoral region. Chemical immobilization was performed using zolazepam tiletamine (5 mg/kg IM). Fine-needle aspiration cytology suggested atypical glandular hyperplasia consistent with carcinoma, prompting surgical excision. Histopathology confirmed tubulopapillary carcinoma. Postoperative recovery was uneventful, and complete wound healing was achieved within two weeks with no recurrence during a six-month follow-up period. This report highlights the clinical presentation, diagnostic approach, surgical management, and pathological findings of a rare mammary carcinoma in a sloth bear.