Mammary tumors are the most prevalent neoplasms in non-neutered female dogs, with genetic and epigenetic alterations contributing to canine mammary carcinogenesis. This study quantified global DNA methylation in 5-methylcytosine (5mC)-immunostained canine mammary tumor samples and established histopathological and clinical correlations. A total of 91 formalin-fixed paraffin-embedded mammary tumor samples from female dogs were retrospectively selected and subjected to immunohistochemistry using an anti-5mC mouse monoclonal antibody. We evaluated 5mC+ stained nuclei of neoplastic epithelial cells in canine mammary glands to obtain semiquantitative histoscores based on staining intensity. Survival rates were estimated based on owners' or veterinary records. Histological samples comprised 28 and 63 benign and malignant canine mammary gland tumors, respectively. Results revealed significant differences between global DNA methylation patterns when mammary samples were categorized as benign or malignant (p = 0.024), with hypomethylated patterns more prevalent in malignant tumors and those with higher relapse behavior (p = 0.011). Of note, large diameter (>5 cm) tumors revealed a lower methylation pattern (p = 0.028). Additionally, we found non-statistically significant differences when tumors were grouped by histopathological characteristics, clinical parameters, or survival. These findings propose global DNA methylation assessment as a promising tool for detecting canine mammary tumors with relapse propensity.

乳腺肿瘤是非中性雌性狗中最普遍的肿瘤，其遗传和表观遗传学改变有助于犬的乳癌发生。这项研究量化了5-甲基胞嘧啶（5mC）-免疫染色的犬乳腺肿瘤样品中的总体DNA甲基化，并建立了组织病理学和临床相关性。回顾性选择来自雌性狗的总共91个福尔马林固定的石蜡包埋的乳腺肿瘤样品，并使用抗5mC小鼠单克隆抗体进行免疫组织化学。我们评估了犬乳腺中肿瘤上皮细胞的5mC +染色核，以基于染色强度获得半定量组织分数。根据所有者或兽医的记录估算存活率。组织学样本包括28和63例良性和恶性犬乳腺肿瘤，分别。结果显示，当乳腺样本被分类为良性或恶性时，总体DNA甲基化模式之间存在显着差异（p = 0.024），低甲基化模式在恶性肿瘤和复发行为较高的肿瘤中更为普遍（p= 0.011）。值得注意的是，大直径（> 5 cm）肿瘤显示出较低的甲基化模式（p= 0.028）。此外，当根据组织病理学特征，临床参数或生存率对肿瘤分组时，我们发现非统计学上的显着差异。这些发现提出了全球DNA甲基化评估作为检测具有复发倾向的犬乳腺肿瘤的有前途的工具。