title: Tumors and tumor-like lesions in the mammary gland of 24 pet rabbits: a histomorphological and immunohistochemical characterization.
abstract: The aim of this retrospective study (2004-2011) was to examine mammary tumors and tumor-like lesions in 24 pet rabbits by histopathology and immunohistochemistry. Rabbits were aged 2 to 8 years. Seventeen were female and 7 female-spayed. Diagnosed tumor-like lesions were lobular hyperplasia (2 rabbits) and multiple cysts (10 rabbits). Tumors included cystadenoma (7 tumors; 3 rabbits), intraductal papilloma (2 tumors; 1 rabbit), intraductal papillary carcinoma (1 tumor), adenocarcinoma (14 tumors; 13 rabbits), adenosquamous carcinoma (2 tumors; 2 rabbits), and matrix-producing carcinoma (1 tumor). The most frequently diagnosed lesion was invasive carcinoma (n = 17). Ten rabbits had several lesions. Immunohistochemistry for calponin and p63 showed that the diagnosed tumor-like lesions, benign tumors, and noninvasive carcinoma had a peripheral myoepithelial layer that was lacking in the invasive carcinomas. In 13 of 14 (93%) of the invasive carcinomas, however, there were variable numbers of calponin- and/or p63-immunopositive cells ranging from 0.1% to 40% with morphological features of either retained nonneoplastic myoepithelial cells or neoplastic epithelial cells with a myoepithelial differentiation. Tumor recurrence was reported in the rabbit with the matrix-producing carcinoma and in 3 rabbits with mammary adenocarcinomas displaying ≥20 mitotic figures in 10 high-power fields and high numbers of neoplastic cells with a myoepithelial differentiation (19%-39%). The rabbit with the matrix-producing mammary carcinoma developed cutaneous metastases confirmed by histopathology. This study shows that different types of mammary tumor-like lesions and tumors can occur in pet rabbits.
authors.affiliation: Institute of Pathology, Faculty of Veterinary Medicine, University of Leipzig, An den Tierkliniken 33, 04103 Leipzig, Germany. Email: sandra.schoeniger@vetmed.uni-leipzig.de.
authors.forename: S
authors.initials: S
authors.lastname: Schöniger
authors.forename: L-C
authors.initials: LC
authors.lastname: Horn
authors.forename: H-A
authors.initials: HA
authors.lastname: Schoon
mesh_terms: D000818:Animals; D002277:Carcinoma / Q000473:pathology / Q000662:veterinary*; D005260:Female; D007150:Immunohistochemistry / Q000662:veterinary; D015674:Mammary Neoplasms, Animal / Q000473:pathology*; D057805:Pets; D011817:Rabbits; D012189:Retrospective Studies; D011795:Surveys and Questionnaires
keywords: immunohistochemistry; mammary gland; myoepithelial cells; rabbit; tumors and tumor-like lesions