Mammary gland malignant myoepithelioma in a domestic rabbit (Oryctolagus cuniculus)
Silva, Halana do CarmoOliveira, Ayisa Rodrigues deHorta, Rodrigo dos SantosMonteiro, Betânia SouzaSilveira, Tatiany LuizaCassali, Giovanni DantasFlecher, Mayra Cunha
Background: Malignant myoepithelioma is a rare neoplasm in humans and rats, poorly reported in dogs and not previously described in rabbits. This study aimed to report a case of malignant mammary myoepithelioma in a domestic rabbit(Oryctolagus cuniculus).Case: A domestic, hybrid, female, entire, nulliparous, 7-year-old rabbit was attended in the Veterinary Hospital Prof. Ricardo Alexandre Hippler at Universidade Vila Velha (UVV) with a history of apathy, lethargy and anorexia. In the clinicalexamination a 5 cm tumour was observed in the right abdominal mammary gland (M2), along with floating smaller lesionsin M1 and M3. There were no palpable abnormalities in the axillary and inguinal lymph nodes. Complete blood count andserum biochemistry were within the normal range. Fine needle aspiration was performed for cytopathological evaluationof the tumour in M2 and it was suggestive of a malignant glandular neoplasm, with probable epithelial origin. Completestaging included chest and abdominal radiographs, but they were unremarkable. The patient was submitted to a rightunilateral mastectomy, involving resection of the inguinal lymph node. The sample was sent to the Laboratory of AnimalPathology of UVV for routine histological evaluation. Histopathological evaluation in M2 was compatible with malignantmyoepithelioma based on the literature, while nodules in M1 and M3 were classified as mammary cysts. The inguinal lymphnode showed no significant abnormalities. An immunohistochemical panel was performed in the Comparative PathologyLaboratory of the Institute of Biological Sciences of the Universidade Federal de Minas Gerais (UFMG), using immunomarkers (pan-cytokeratin, p63 and vimentin) to characterize the tumour and confirm its diagnosis. Immunohistochemistryrevealed expression of p63, and was negative for pan-cytokeratin and vimentin, which confirmed the myoepithelial origin,without involvement of the epithelial compartment...(AU)
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