Mammary carcinoma in a mare: clinical, histopathological and steroid hormone receptor status.

Summary The aim of this paper is to describe the clinical, histopathological and immunohistochemical findings of a mammary carcinoma in a 22-year-old, 10 month pregnant, thoroughbred mare. The clinical examination of the right mammary gland showed a firm enlargement and purulent discharge from the ulcerated skin surface and the teat. During necropsy visceral metastases were not found but inguinal lymph nodes presented metastatic infiltrations when observed histologically. None of the previous reports found positive immunohisthochemical reactions for estrogen and progesteron receptors in an equine mammary adenocarcinoma. However, the findings of positive immunoreactivity to steroid receptors could suggest a hormonal influence on the genesis of the mammary neoplasm, as demonstrated in human breast cancer. der neoplastischen Epithelzellen festgestellt. In dem noch gesundem Gesäugegewebe gab es eine positive Reaktion auf Östrogenrezeptoren und auf Progesteronrezeptoren. Dieser erste Fall eines positiven immunhistochemischen Steroid-hormonrezeptornachweises beim Pferd könnte für einen hormonellen Einfluss bei der Genese der Mammatumoren sprechen, wie es bei Mammatumoren des Menschen bekannt ist.