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.

一只 12 岁雌性芬兰-设得兰杂交羊的一个大而坚硬的多囊性乳腺肿块在 4 年内缓慢生长。初步观察后 30 个月进行细针抽吸细胞学检查，怀疑上皮恶性肿瘤的诊断。 18个月后，当羊群规模缩小时，这只羊被安乐死。现场尸检发现有一个巨大的乳腺肿块，但没有转移到内脏器官。乳腺组织的印记细胞学支持良性增殖过程。组织学上，乳腺组织被乳腺上皮的囊性、管状和乳头状腺瘤排列所消除，具有间变性成分，与腺瘤中产生的乳腺癌一致。 IHC 显示抗孕激素受体抗体呈强核阳性，抗雌激素受体α表达抗体呈极低阳性。通过调整伴侣动物 IHC 分类组，尝试对基底或管腔上皮起源进行内在亚型分型；高分子量和低分子量细胞角蛋白（CK5、CK8、CK18）未能染色，但基底上皮 p63 表达呈阳性。