探讨子宫癌肉瘤 (UCS)的临床病理学特征、免疫表型、诊断和鉴别诊断，以及UCS的基因突变特征和肿瘤突变负担 (TMB)。回顾性分析苏州大学附属第二医院病理科自2021年1月至2022年5月所归档的4例UCS的临床影像、病理形态学数据和免疫组化表达。对4例UCS的所有外显子组进行了测序。这4名患者均为女性，年龄为47-81岁。肿瘤的最大直径为4.0-13.0 cm，边界不清晰。镜下，肿瘤由恶性上皮和肉瘤组成。免疫组化显示，4名患者的上皮成分表达广谱细胞角蛋白 (AE1/E3)，肉瘤成分表达Vimentin，PAX8，ER，PR的表达程度不同，并且Ki-67阳性指数较高 (60%-90%)。其中有3例p53错义突变，1例无义突变，4例MLH1，PMS2，MSH2，MSH6均为阳性，PD-L1为阴性。4例UCS患者的整个外显子组测序结果显示，TP53、BCL9L、BRD4、CLTCLI、PSMD1I、PLEC基因的突变率较高，分别为3/4、2/4、2/4、2/4、2/4、2/4。TMB分析显示，4例UCS的TMB <5 mut/Mb。UCS是一种罕见且高度恶性的子宫内膜肿瘤。整个外显子组测序结果提示，TP53、BCL9L、BRD4等基因具有高突变率，表明UCS的发生和发展可能与Wnt信号通路密切相关。分子分型表明，3例UCS为高拷贝数型/p53突变型，1例为POLD1突变。微卫星稳定性、低PD-L1表达和TMB结果提示，UCS患者在免疫治疗方面没有明显优势。

To explore the clinicopathological characteristics, immunophenotype, diagnosis and differential diagnosis of uterine carcinosarcoma (UCS), and to explore the gene mutation characteristics and tumor mutation burden (TMB) of UCS. The clinical imaging, pathomorphological data and immunohistochemical expression of 4 cases of UCS, which were archived in the Department of Pathology of the Second Affiliated Hospital of Soochow University from January 2021 to May 2022 were retrospectively analyzed. All exon groups of 4 cases of UCS were sequenced. All the 4 patients were female, aged 47-81 years. The maximum diameter of the tumor was 4.0-13.0 cm, and the boundary was unclear. Microscopically, the tumor was composed of malignant epithelium and sarcoma. Immunohistochemistry showed that the epithelial components of 4 patients expressed broad-spectrum cytokeratin (AE1/E3), the sarcoma components expressed Vimentin, PAX8, ER, PR were expressed to varying degrees, and Ki-67 positive index was high (60%-90%). There were 3 p53 missense mutations, 1 nonsense mutation, 4 MLH1, PMS2, MSH2, MSH6 were positive and PD-L1 was negative. The sequencing results of the whole exon group of 4 UCS patients showed that TP53, BCL9L, BRD4, CLTCLI, PSMD1I, PLEC genes showed a high mutation ratio, which was 3/4, 2/4, 2/4, 2/4, 2/4, 2/4, respectively. TMB analysis showed that the TMB of 4 cases of UCS was<5 mut/Mb. UCS is a rare and highly malignant endometrial tumor. The sequencing results of the whole exon group suggested that TP53, BCL9L, BRD4 and other genes had high mutation rates, suggesting that the occurrence and development of UCS may be closely related to Wnt signaling pathway. Molecular typing indicated that 3 cases of UCS were of high copy number type/p53 mutation type, and 1 case had POLD1 mutation. Microsatellite stability, low PD-L1 expression and TMB results suggested that UCS patients have no obvious advantage in immunotherapy.