A variety of tissues in bone can be the origin of neoplastic primitive lesions. Consequently, it can be the site of various sarcomas of tissue type, incursing leiomyosarcoma. The leiomyosarcoma of the bone is considered as primitive after exclusion either a bony extension of a soft tissue tumor of vicinity or the presence of a leiomyosarcoma elsewhere. We report a case of a primary leiomyosarcoma arising on the left femur of a 40-year-old woman. The diagnosis was confirmed by immuno-histochemistry and electron microscopic study. A bloc resection followed by a prothesis was performed. The patient underwent a fractioned postoperative radiotherapy with a total dose of 75 Gy. The postoperative course one year later revealed local recurrence and pulmonary metastases. Despite the resection of pulmonary metastases and the amputation of left lower limb, the patient had developed local recurrence on the stump of amputated limb and was on the outside of all therapeutic resource. In this report, we present the clinicopathologic, immuno-histochemical and ultrastructural profiles of these rare primary bone tumors.