Summary Leiomyosarcoma is an aggressive sarcoma thought to arise from the smooth muscle cells lining small blood vessels. The condition usually presents in patients in the 5th and 6th decades of life, with pain and a palpable mass. Diagnosis is made with biopsy showing a spindle cell neoplasm with similar characteristics shared between the osseous and soft tissue forms of this disease. Immunostains are positive for actin and vimentin. Treatment is generally wide surgical resection with radiation. Epidemiology Incidence fewer than 100 case reports of extra-facial leiomyosarcoma of bone Demographics the mean age of presentation is in 5th and 6th decades of life Anatomic location most frequently occurs in the metaphysis of long bones, but can occur in diaphyseal locations. the most frequent sites of boney presentation are the femur, tibia, ilium, and humerus Presentation Symptoms bone pain palpable mass typical duration of symptoms prior to diagnosis is 6 months Physical exam pelvic masses can be difficult to appreciate on inspection exam can be tender or nontender to palpation masses will be firm Imaging Radiographs involved extremity purely osteolytic lesions with ill-distinct margins, moth-eaten, or permeative pattern of bone destruction. primarily intra-medullary but may extend into the soft tissues. chest indicated for all staging of tumors to evaluate for lung metastasis CT indications help evaluate bone loss of involved extremity or pelvis chest CT indicated in all patients as part of staging workup to evaluate for metastasis MRI indications differentiate from benign soft tissue tumors evaluate size, depth, and surrounding anatomy views appears dark on T1, similar to muscle tissue appears heterogeneous on T2 with areas of increased signal intensity contrast causes diffuse enhancement of signal within the lesion Studies Histology a spindle cell neoplasm with similar characteristics shared between the osseous and soft tissue forms of this disease cigar-shaped nuclei cells arranged into fascicles along with myofibrils running parallel presence of actin and vimentin immunoreactivity Staging all tumors should be staged appropriately prior to treatment initiation Treatment Nonoperative chemotherapy indications diffuse metastatic disease to the lungs large pelvic masses with neurovascular involvement that preclude safe resection outcomes variable response to chemotherapy better survival when chemotherapy combined with surgery than surgery alone radiation indications controversial contaminated resection bed outcomes variable response, difficult to predict Operative early wide resection of the primary lesion and secondary reconstruction indications standard of care in localized disease technique clean margin is an important goal of surgical resection chemotherapy Neo-adjuvant or adjuvant chemo/radiotherapy in the treatment of leiomyosarcoma of bone is controversial radiation if unable to obtain wide margin consider adjuvant radiation Prognosis LMS of bone in adults 25% recurrence rate and 25% metastasis rate 75% survival at 3 years with treatment