Department of Pathology and Laboratory Medicine, Lifespan Medical Center and Brown University Alpert School of Medicine, Providence, RI.
Appl Immunohistochem Mol Morphol. 2021 Apr 1;29(4):293-298. doi: 10.1097/PAI.0000000000000883.
PAX8 expression is frequently detected in renal, thyroidal, and Müllerian carcinomas, and PAX8 immunohistochemistry is often used to confirm the origin of these tumors. Tumors metastatic to the breast may masquerade as primary breast lesions. PAX8 is strongly expressed in tumors of Müllerian origin and largely negative in breast primaries, but an immunohistochemical expression of PAX8 in breast cancer has not been systematically evaluated in a large series. We analyzed 266 cases of invasive carcinoma of the breast on tissue microarrays and whole tissue sections with a PAX8 monoclonal antibody. Both the extent (focal or diffuse) and intensity (weak, moderate, or strong) of nuclear staining were assessed in the tumor cells. In total, 16 cases (6.02%) were positive for PAX8 (12 with weak and 4 with moderate staining). Expression was diffuse in 7 cases and focal in 9 cases. All 16 PAX8-positive tumors were histologic grade III invasive ductal carcinomas, 13 of these were triple-negative, 2 were HER2-positive, only and 1 was progesterone receptor-positive only. Strong PAX8 nuclear expression was not seen in any of the cases. PAX8 was negative in breast tumors with neuroendocrine features. Our study demonstrated a low rate of PAX8 expression in breast cancer. When present, PAX8 expression was only seen in high-grade invasive ductal carcinomas, mostly triple-negative. The presence of PAX8 immunoreactivity alone cannot exclude mammary origin, especially when only weak to moderate staining is observed, so the correlation with available clinical and pathologic data helps to ensure an accurate diagnosis.
PAX8 表达通常在肾脏、甲状腺和 Müllerian 癌中检测到，PAX8 免疫组化常用于确认这些肿瘤的来源。转移到乳腺的肿瘤可能伪装为原发性乳腺病变。PAX8 在 Müllerian 来源的肿瘤中强烈表达，而在乳腺原发性肿瘤中大部分为阴性，但在大系列中尚未系统评估 PAX8 在乳腺癌中的免疫组化表达。我们使用 PAX8 单克隆抗体在组织微阵列和全组织切片上分析了 266 例浸润性乳腺癌病例。评估肿瘤细胞中的核染色程度（局灶性或弥漫性）和强度（弱、中或强）。总共有 16 例（6.02%）PAX8 阳性（12 例为弱阳性，4 例为中度染色）。16 例 PAX8 阳性肿瘤均为组织学分级 III 级浸润性导管癌，其中 13 例为三阴性，2 例为 HER2 阳性，仅 1 例孕激素受体阳性。在任何病例中均未观察到强 PAX8 核表达。PAX8 在具有神经内分泌特征的乳腺肿瘤中为阴性。我们的研究表明乳腺癌中 PAX8 表达率较低。当存在时，PAX8 表达仅见于高级别浸润性导管癌，大多数为三阴性。单独存在 PAX8 免疫反应性不能排除乳腺来源，尤其是当仅观察到弱至中度染色时，因此与现有临床和病理数据的相关性有助于确保准确诊断。
