骨外骨肉瘤是发生于软组织的骨肉瘤，临床上少见，现将我院收治并经病理证实的1例报告如下。患者男，55岁。左大腿中下段前内侧肿物4个月，伴局部疼痛2周入院，无外伤史及夜间痛。查体：左大腿中下段前内侧可触及一12 cm×10cm肿物，质韧，边界尚清，有轻压痛，活动可，皮温不 Osteosarcoma in the bone is an osteosarcoma that occurs in soft tissue. It is clinically rare, and one case that is admitted to our hospital and confirmed by pathology is as follows. Male patient, 55 years old. Left medial thoracic anterior medial mass 4 months, with local pain 2 weeks admission, no history of trauma and night pain. Physical examination: the middle of the left thigh before the medial touch of a 12 cm × 10cm mass, quality and tough, clear border, mild tenderness, activity can be, skin temperature is not