子宫癌肉瘤（UCS）是一种罕见的高级别子宫内膜癌，治疗选择有限。我们评估了大型 UCS 队列中人表皮生长因子受体 2 (HER2) 表达和 HER2 基因扩增的预后意义，并阐明了 HER2 低 UCS 的临床病理特征。我们使用体内诊断技术检查了 148 名 UCS 患者的 HER2 蛋白表达对72例患者进行HER2免疫组织化学（IHC）试剂盒和使用荧光原位杂交（FISH）的HER2基因扩增。HER2 IHC评分根据最新的美国临床肿瘤学会/美国病理学家学院胃癌标准进行评估，2017年为阴性。 41例患者中，57例患者中观察到1例低表达，50例患者中观察到HER2高表达（38例中2例，12例中3例）。基于HER2蛋白表达状态的临床病理特征无显着统计学差异。 HER2 阴性和低表达与高表达相比显示 I/II 期总体生存率较差。与其他癌症类型相比，IHC 和 FISH 结果之间的一致性相对较低（HER2 IHC 评分 1、2 和 3 分别为 5%、15% 和 50%），并且将这些结果结合起来作为 UCS 的预后因素并不有效。相比之下，HER2 IHC 评分单独是 I/II 期 UCS 的预后因素。 HER2 低组没有表现出特定的临床病理特征。由于晚期 UCS 中 HER2 IHC 评分低是一个预测因素，因此在不久的将来可能会建议使用 HER2 IHC 评分对 HER2 IHC 评分低组进行 UCS 分层并开发辅助治疗。© 2025。亚洲妇科肿瘤学会、韩国妇科肿瘤学会和日本妇科肿瘤学会。

Uterine carcinosarcoma (UCS) is uncommon high-grade endometrial cancer with limited treatment options. We evaluated the prognostic significance of human epidermal growth factor receptor 2 (HER2) expression and HER2 gene amplification within large cohorts of UCS, and clarify clinicopathologic characteristics of HER2-low UCS.We examined HER2 protein expression in 148 patients of UCS using in vivo diagnostic HER2 immunohistochemistry (IHC) kits and HER2 gene amplification using fluorescence in situ hybridization (FISH) in 72 patients.HER2 IHC score was evaluated according to the latest American Society of Clinical Oncology/College of American Pathologists criteria for gastric cancer, which was negative in 41 patients, low expression of 1+ was observed in 57 patients, and HER2 high expression was observed in 50 patients (2+ in 38 and 3+ in 12 patients). There was no significant statistical difference in clinicopathological characteristics based on HER2 protein expression status. HER2 negative and low expression compared to high expression revealed poor overall survival in stage I/ II. The concordance between IHC and FISH results were relatively low compared to other cancer types (HER2 IHC score 1+, 2+, and 3+ were 5%, 15%, and 50%), and combining these results was not efficient as a prognostic factor in UCS. In contrast, the HER2 IHC score alone was a prognostic factor in stage I/II UCS. HER2 low group did not show specific clinicopathologic features.Since the HER2 IHC score low in advanced UCS is a predictive factor, stratification of UCS using HER2 IHC score for HER2 IHC score low group and developing adjuvant therapy may be proposed in the near future.© 2025. Asian Society of Gynecologic Oncology, Korean Society of Gynecologic Oncology, and Japan Society of Gynecologic Oncology.