Mammary carcinoma arising in an adenoma in a ewe

Abstract

A large, firm, multi-cystic mammary gland mass grew slowly over 4 y in a 12-y-old, female Finn–Shetland cross sheep. A diagnosis of epithelial malignancy was suspected following fine-needle aspiration cytology at 30 mo after initial observation. The sheep was euthanized when the flock was downsized 18 mo later. A field postmortem examination revealed a large mammary mass, but an absence of metastases to internal organs. Imprint cytology of the mammary tissue supported a benign proliferative process. Histologically, mammary tissue was obliterated by cystic, tubular, and papillary adenomatous arrangements of mammary epithelium, with an anaplastic component, consistent with mammary carcinoma arising in an adenoma. IHC showed strong nuclear positivity to the antibody against progesterone receptor and minimal positivity to the antibody against estrogen receptor alpha expression. Intrinsic subtyping for basal or luminal epithelial origin was attempted through adaptation of companion animal IHC classification panels; high- and low-molecular-weight cytokeratins (CK5, CK8, CK18) failed to stain, but p63 expression for basal epithelium was positive.

An ovine model for investigation of the microenvironment of the male mammary gland

“…This observation, together with the well-documented histo-anatomical similarities of the sheep mammary gland to the human breast (Hughes, 2021b; Nagy et al, 2021; Rowson et al, 2012) indicate that the male sheep mammary gland may be a useful adjunctive model of the male human breast. As mammary tumourigenesis is rare in sheep (Hughes, 2021b; Newman et al, 2021), the male ovine gland does not offer a direct model for male breast cancer, but it will facilitate furthering understanding of normal male mammary biology to use in comparative studies. In addition, the relative resistance of the sheep to development of mammary tumours may be a further fruitful avenue of future comparative study (Hughes, 2023).…”

An ovine model for investigation of the microenvironment of the male mammary gland

“…This observation, together with the well-documented histo-anatomical similarities of the sheep mammary gland to the human breast (Hughes, 2021b;Nagy et al, 2021;Rowson et al, 2012) indicate that the male sheep mammary gland may be a useful adjunctive model of the male human breast. As mammary tumourigenesis is rare in sheep (Hughes, 2021b;Newman et al, 2021;Rauner, 2024), the male ovine gland does not offer a direct model for male breast cancer, but it will facilitate furthering understanding of normal male mammary biology to use in comparative studies. In addition, the relative resistance of the sheep to development of mammary tumours may be a further fruitful avenue of future comparative study (Hughes, 2023).…”