Canine mammary tumors (CMT) represent the most common neoplasms in female dogs and their diagnosis and classification relies on histopathological examination. Recently, PGRMC1 has been considered to be a putative biomarker for diagnosis and prognosis in many human cancers as it is expressed in a wide variety of tumors. This study represents the first description of PGRMC1 expression in CMT. PGRMC1 expression was initially assessed by immunohistochemistry in healthy or hyperplastic tissues and in four major histopathological types of CMT: simple and complex adenomas and carcinomas. PGRMC1 staining was represented by a scoring system that considered the percentage of positive cells and staining intensity. PGRMC1 expression was defined as either weak, moderate or strong. In healthy and hyperplastic tissues almost 100% of the epithelial cells stained intensely for PGRMC1. Adenomas showed similar features but with a more variable intensity. In tubular areas of adenocarcinomas, a lower percentage of epithelial cells (30–60%) stained for PGRMC1 with a weak intensity. Both the percentage of cells and intensity of PGRMC1 staining became progressively negative in the solid parts of the tumor. Western blot analysis of healthy and neoplastic mammary tissue (carcinomas samples) revealed the presence of the 25 kDa PGRMC1 band in both types of tissue, while the 50 kDa form was mainly detected in the healthy counterpart. This study reveals that PGRMC1 is expressed in CMT and its expression pattern changes depending on the pattern of growth of CMT. Further studies are now needed to determine PGRMC1's putative role and usefulness for typing and prognosis of different CMT subtypes.

犬乳腺肿瘤（CMT）是母犬中最常见的肿瘤，其诊断和分类取决于组织病理学检查。近来，由于PGRMC1在多种肿瘤中表达，因此被认为是许多人类癌症中诊断和预后的推定生物标志物。这项研究代表在CMT中PGRMC1表达的首次描述。最初通过免疫组织化学方法在健康或增生组织以及四种主要的CMT组织病理学类型（简单和复杂的腺瘤和癌）中评估了PGRMC1的表达。PGRMC1染色由计分系统表示，该计分系统考虑了阳性细胞的百分比和染色强度。PGRMC1表达被定义为弱，中或强。在健康和增生组织中，几乎100％的上皮细胞都被PGRMC1强烈染色。腺瘤表现出相似的特征，但强度变化更大。在腺癌的肾小管区域，PGRMC1染色的上皮细胞百分比较低（30-60％），强度较弱。在肿瘤的实体部分中，细胞百分比和PGRMC1染色强度都逐渐变为阴性。对健康和赘生性乳腺组织（癌样品）的蛋白质印迹分析表明，两种组织中均存在25 kDa PGRMC1条带，而50 kDa形式主要在健康对应物中检测到。这项研究表明，PGRMC1在CMT中表达，其表达方式根据CMT的生长方式而变化。现在需要进一步研究以确定PGRMC1'