Surgical, histological, and immunohistochemical approach to spontaneous malignant mammary tumor in a fancy rat (Rattus norvegicus domestica): a case report

Abstract A domestic rat ( Rattus norvegicus domestica ) was presented to the Department of Veterinary Medicine of the University of Bari “Aldo Moro” (Bari, Italy) for the presence of a progressive growing unilateral mass. The mass was completely surgically removed, and then histologically and immohistochemically evaluated. The lesion was diagnosed as mammary ductal carcinoma based on histopathological examination. Immunohistochemistry staining for estrogen receptor alpha (ERα) and proliferation marker Ki-67 were found to be positive. The rat was rechecked 3 months thereafter, with total body radiographs taken for metastatic assessment, and no macroscopic evidence of tumor recurrence was observed at the surgical site. Thus, the most effective weapon remains prevention, so owners should be advised to timely spay their pets to reduce the probability of mammary tumor appearance.