The purpose of this study was to evaluate a possible association between mammary tumour size and increasing degree of malignancy. Data of 625 dogs with a total of 1459 mammary tumours were analysed retrospectively. 80.3% dogs were intact, mean age at diagnosis was 9.7 ± 2.5 years, 75.8% were pure breed dogs. Median body weight was 20.0 kg. Malignant tumours (n = 580) were significantly larger than their benign counterparts (1.94 cm vs 0.90 cm in mean, respectively; P ≤ .0001), resulting in a positive correlation between increasing tumour size and a change from benign to malignant (P ≤ .0001; r_s = 0.214). When malignant tumours were grouped into four degrees of increasing malignancy (complex/simple/solid/anaplastic carcinomas) a significant positive correlation between increasing tumour size and more malignant tumour degree (P ≤ .0001; r_s = 0.195) could be demonstrated. In a number of cases, highly malignant tumours were found to arise within less malignant lesions, supporting the concept of a further progression within the malignant tumour subtypes. In patients with multiple tumours, mean tumour sizes for malignant tumours were significantly smaller compared to patients with only one tumour (1.67 vs 2.71 cm in mean, respectively; P < .0001). These findings suggest that mammary tumours progress not only from benign to malignant but also from low to highly malignant. An increase in diameter of only a few millimetres may therefore have a big impact on the patient's outcome.

中文翻译：

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犬类乳腺肿瘤：大小很重要——从低度恶性到高度恶性亚型的进展

本研究的目的是评估乳腺肿瘤大小与恶性程度增加之间可能存在的关联。回顾性分析了625只犬共1459个乳腺肿瘤的数据。80.3% 的狗完好无损，诊断时的平均年龄为 9.7 ± 2.5 岁，75.8% 是纯种狗。中位体重为20.0 kg。恶性肿瘤（n = 580）显着大于其良性对应物（分别为 1.94 厘米和 0.90 厘米；P  ≤ .0001），导致肿瘤大小增加与从良性到恶性的变化呈正相关（P  ≤ .0001; r _s = 0.214)。当将恶性肿瘤分为四个恶性程度增加（复杂/简单/实体/间变性癌）时 ，可以证明肿瘤大小增加与恶性程度增加之间存在显着正相关（ P  ≤ .0001；r _{s = 0.195）。}在许多情况下，发现高度恶性的肿瘤出现在恶性程度较低的病灶中，这支持了恶性肿瘤亚型内进一步进展的概念。在患有多发肿瘤的患者中，恶性肿瘤的平均肿瘤大小明显小于只有一个肿瘤的患者（分别为 1.67 和 2.71 厘米；P < .0001)。这些发现表明，乳腺肿瘤不仅从良性发展到恶性，而且从低度恶性发展到高度恶性。因此，直径仅增加几毫米可能会对患者的结果产生重大影响。