目的　研究横纹肌肉瘤的形态学 ,阐明诊断和鉴别诊断。方法　分析 40例横纹肌肉瘤的组织类型、形态和免疫组化。结果　分为 3种亚型 ,胚胎型横纹肌肉瘤 2 0例 ,含有星形、梭形和小圆形细胞形 ;腺泡状横纹肌肉瘤16例 ,以小圆形细胞及中圆形细胞为主 ;多形性横纹肌肉瘤 4例 ,多为大圆形及中圆形细胞。全部肿瘤中 ,带状细胞 ,蝌蚪形细胞及多核细胞占 2 7% ,仅 1例见到横纹。免疫组化阳性率分别为 :Vimentin 92 % ,desmin 5 3.3% ,平滑肌肌动蛋白 87.5 %及Myoglobin 92 .2 %。结论　在横纹肌肉瘤中少数为带状及蝌蚪状细胞 ,绝大多数为圆形细胞 ,后者具有重要诊断价值 ,免疫组化能增加诊断的正确性 Objective To study the morphology of rhabdomyosarcoma and clarify the diagnosis and differential diagnosis. Methods The histological type, morphology and immunohistochemistry of 40 cases of rhabdomyosarcoma were analyzed. The results were divided into three subtypes, embryonal rhabdomyosarcoma in 20 cases, containing star, spindle and small round cell shape; 16 cases of alveolar rhabdomyosarcoma, mainly small round cells and round cells; There were 4 cases of pleomorphic rhabdomyosarcoma, mostly large round and medium round cells. In all tumors, zonal cells, sickle-shaped cells and multinucleated cells accounted for 27%, and only 1 case saw transverse stripes. The positive rates of immunohistochemistry were: Vimentin 92%, desmin 5 3.3%, smooth muscle actin 87.5 % and Myoglobin 92.2%. Conclusion Among the rhabdomyosarcomas, few are ribbons and sickle cells, most of which are round cells. The latter has important diagnostic value. Immunohistochemistry can increase the accuracy of diagnosis.