Rabbit tumor case highlights risks of sex misidentification

A case report published online April 27 in the Journal of Veterinary Diagnostic Investigation describes a 5-year-old Holland Lop rabbit that had been presumed male, based on a small penis-like structure and pet store information, but was later found to have a malignant paramesonephric, or Müllerian, tumor associated with uterine-like tissue. Imaging showed a large caudal abdominal mass, exploratory surgery led to excision, and histopathology plus immunohistochemistry supported the diagnosis. PCR testing did not detect Y-linked genes including SRY, ZFY, and RBMY, suggesting the rabbit was genetically female. No gonadal structures were identified on imaging or during surgery. The rabbit initially improved after surgery, then died two weeks later from severe rhinitis rather than the tumor itself. (journals.sagepub.com)

Why it matters: For veterinary professionals, the report is a reminder that reproductive tract disease in rabbits can be missed when sex has been incorrectly assigned, especially in patients with atypical external anatomy or incomplete history. That matters because uterine neoplasia is already a major concern in intact female rabbits, with standard references describing uterine adenocarcinoma as the most common tumor in rabbits and recommending attention to reproductive disease as rabbits age. This case broadens the differential list beyond the more familiar uterine adenocarcinoma and highlights the value of correlating imaging, surgical findings, histopathology, and, when anatomy is unclear, molecular sex testing. (journals.sagepub.com)

What to watch: Whether this report prompts more routine use of confirmatory sex determination, including imaging or genetic testing, in rabbits with atypical genital findings or unexplained caudal abdominal masses. (journals.sagepub.com)