目的 总结先天性中胚层肾瘤的临床病理学特征、免疫表型及鉴别诊断。方法 分析4例先天性中胚层肾瘤的临床病理特征并进行相关的文献复习。结果 肿瘤均发生于2岁以下小儿，大体呈包膜完整的肿块，镜下4例均为经典型，由一致的梭形细胞组成，呈束状或编织状排列，细胞稀疏区呈网状排列，细胞核细长，核仁不明显，核分裂像3～5个/10 高倍视野，瘤细胞间可见少量不规则分布的残存肾组织。免疫组织化学示肿瘤细胞呈波形蛋白阳性和平滑肌肌动蛋白部分阳性。经过随访未见肿瘤转移及复发。结论 先天性中胚层肾瘤是发生在婴幼儿肾脏的低度恶性肿瘤，组织形态学表现为一致性的梭形细胞，部分显示肌纤维母细胞分化，手术完整切除后预后良好。

Objective To investigate the clinicopathological characteristics, immune phenotype and differential diagnosis of congenital mesoblastic nephroma. Methods The clinicopathological characteristics of 4 cases of congenital mesoblastic nephroma were analysed, and related literatures were reviewed. Results The tumors occurred in children younger than 2 years old, generally presenting a capsular complete lump. All the 4 cases were classical congenital mesoblastic nephroma. The tumors consisted of spindle cells with elongated nucleus. Tumors grew with a bunch or woven pattern. The cells arranged net-like in sparse area, with elongated nucleus, obvious nucleoli and nuclear fission of 3-5/10 HPF. A small amount of irregular distribution of the remaining kidney tissues was found between the tumor cells. Immunohistochemistry indicated that there were positive expression of vimentin and partially positive expression of smooth muscle actin in the tumor cells. No tumor recurrence or metastasis was observed during follow-up. Conclusion Congenital mesoblastic nephroma is a low-grade malignant tumor in infants and young children, which exhibits spindle cells in histomorphology. The prognosis may be favorable after complete resection.