原发于骨骼的平滑肌肉瘤很少见 ,发生在扁骨的更为罕见 ,笔者遇见 1例 ,报告如下。患者　女 ,30岁。主因左腰部肿物伴疼痛 3个月入院。患者于 2年前曾因左腰部肿物在当地医院手术切除 ,病理诊断 :纤维组织增生。体检 :左下腰部饱满 ,可触及一个肿物约 10ｃｍ× 10ｃｍ× 8ｃｍ Primary in the skeleton of leiomyosarcoma is rare, occurred in the flat bones are more rare, I met one case, the report is as follows. Female patient, 30 years old. Main left lumbar mass with pain 3 months admitted. The patient was surgically removed from the left lumbar mass 2 years ago at a local hospital. Pathological diagnosis: Fibrous tissue hyperplasia. Physical examination: full of left lower back, can reach a tumor about 10cm × 10cm × 8cm