Feline mammary tumors are usually malignant and aggressive carcinomas. Most cases are simple monophasic carcinomas (1 epithelial population), and additional phenotyping is usually not needed. In this study, we describe 10 malignant mammary tumors from 9 female cats that had unusual histomorphology: they appeared biphasic, with 2 distinct cell populations. Initially, they were morphologically diagnosed as either carcinosarcoma (1/10) or malignant pleomorphic tumor (9/10) of the mammary gland, as the latter did not match any previously described histological subtype. Immunohistochemistry (IHC) was performed for pancytokeratin, cytokeratins 8 and 18, cytokeratin 14, cytokeratins 5 and 6, vimentin, p63, calponin, alpha-smooth muscle actin, Ki-67, ERBB2, estrogen receptor alpha, and progesterone receptor. In 7 of 10 cases, the biphasic nature was confirmed and, on the basis of the IHC results, they were classified as carcinoma and malignant myoepithelioma (4/10), ductal carcinoma (1/10), and carcinosarcoma (2/10). The other 3 of 10 cases were monophasic based on IHC. In the cases of carcinoma and malignant myoepithelioma, the malignant myoepithelial cells were 100% positive for vimentin (4/4) and variably positive for p63, calponin, and cytokeratins (4/4). These findings show that, although rare, biphasic mammary carcinomas do occur in cats. In dogs and humans, tumors composed of malignant epithelial and myoepithelial cells have a less aggressive behavior than certain simple carcinomas, and therefore, their identification might also be clinically significant in the cat.

中文翻译：

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双相猫乳腺癌，包括癌和恶性肌上皮瘤。


猫乳腺肿瘤通常是恶性和侵袭性癌症。大多数病例是简单的单相癌（1 个上皮细胞群），通常不需要额外的表型分析。在这项研究中，我们描述了来自 9 只母猫的 10 种恶性乳腺肿瘤，这些肿瘤具有不寻常的组织形态：它们呈现双相性，具有 2 个不同的细胞群。最初，它们在形态学上被诊断为乳腺癌肉瘤（1/10）或恶性多形性肿瘤（9/10），因为后者与任何先前描述的组织学亚型都不匹配。对全细胞角蛋白、细胞角蛋白 8 和 18、细胞角蛋白 14、细胞角蛋白 5 和 6、波形蛋白、p63、钙调蛋白、α-平滑肌肌动蛋白、Ki-67、ERBB2、雌激素受体 α 和黄体酮受体进行免疫组织化学 (IHC)。 10例中有7例确诊为双相性，根据IHC结果，将其分类为癌和恶性肌上皮瘤（4/10）、导管癌（1/10）和癌肉瘤（2/10） 。根据 IHC，10 例中的​​另外 3 例为单相。在癌和恶性肌上皮瘤的病例中，恶性肌上皮细胞波形蛋白 100% 阳性 (4/4)，p63、钙调蛋白和细胞角蛋白呈不同程度的阳性 (4/4)。这些发现表明，虽然罕见，但双相乳腺癌确实发生在猫身上。在狗和人类中，由恶性上皮细胞和肌上皮细胞组成的肿瘤比某些简单的癌症具有较小的侵袭性，因此，它们的识别在猫中也可能具有临床意义。