Benign mammary tumours are among the most common tumours of companion rats (Rattus norvegicus domestica), as well as a major animal welfare concern and euthanasia. The first objective of this study was to evaluate the expression of oestrogen, progesterone, androgen, and prolactin receptors in neoplastic and normal mammary gland tissues and compare the expression of these receptors between groups. The second objective was to determine if the expression of these receptors in neoplastic mammary gland tissue correlates with overall survival and occurrence of an additional mass after initial mammary mass excision. The third objective was to determine if the expression of oestrogen, progesterone, androgen and prolactin receptors was associated with mammary tumor clinical parameters or with the age of the animals. Thirty‐two benign mammary tumours were collected from companion rats and submitted for immunohistochemistry staining of prolactin receptor, oestrogen receptor alpha (ERa), progesterone and androgen receptors (AR). Allred score were obtained for mammary tumours (n = 32) and surrounding normal mammary tissue (n = 20) when present. Prolactin receptor expression increased significantly with mammary gland tumorigenesis (P < .0001), while AR expression decreased with tumorigenesis (P < .0001). Lower expression of ERa in tumor stroma was associated with shorter survival (P = .02). Hormonal receptor expression was not significantly associated with age, mass diameter, location nor likelihood of additional mass development. Further studies should investigate the effects of prolactin antagonists in a prospective study involving companion rats with benign mammary tumours.

中文翻译：

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伴侣大鼠良性乳腺肿瘤中催乳素和雄激素受体表达的改变

良性乳腺肿瘤是伴侣大鼠 (Rattus norvegicus domestica) 最常见的肿瘤之一，也是主要的动物福利问题和安乐死。本研究的第一个目的是评估肿瘤和正常乳腺组织中雌激素、孕激素、雄激素和催乳素受体的表达，并比较这些受体在各组之间的表达。第二个目标是确定这些受体在肿瘤性乳腺组织中的表达是否与总体存活率和初始乳腺肿块切除后额外肿块的发生相关。第三个目标是确定雌激素、孕酮、雄激素和催乳素受体的表达是否与乳腺肿瘤临床参数或动物年龄相关。从伴侣大鼠中收集了 32 只良性乳腺肿瘤，并提交给催乳素受体、雌激素受体 α (ERa)、孕酮和雄激素受体 (AR) 进行免疫组织化学染色。当存在时，获得了乳腺肿瘤（n = 32）和周围正常乳腺组织（n = 20）的 Allred 评分。随着乳腺肿瘤的发生，催乳素受体表达显着增加（P  < .0001），而 AR 表达随着肿瘤发生而降低（P  < .0001）。肿瘤基质中 ERa 的低表达与较短的生存期相关 ( P  = .02)。激素受体表达与年龄、肿块直径、位置或额外肿块发展的可能性没有显着相关性。进一步的研究应在一项涉及患有良性乳腺肿瘤的伴侣大鼠的前瞻性研究中调查催乳素拮抗剂的作用。