Leiomyosarcoma of the tibia. Report of a case

A 48-year-old man with an unremarkable medical history was admitted for a painful swelling over the anteromedial aspect of his right leg. Radiographs disclosed heterogeneity of the proximal tibia, with increased uptake on the bone scan. Computed tomography findings consisted of heterogeneity of the proximal tibial metaphysis and diaphysis with subtle cortical osteolysis, periosteal appositions and soft tissue involvement. Magnetic resonance images showed low signal from the metaphysis, diaphysis and soft tissues on T1 sections that enhanced after gadolinium and converted to high signal on T2 images. Lung metastases were also found. Histologic features were consistent with leiomyosarcoma, which was considered to have originated in the tibia since no other primary localization was found. Combination chemotherapy was successful in eliminating the clinical manifestations and clearing the lung metastases. Six months later, the same chemotherapy regimen failed to improve a local and pulmonary recurrence and the patient died a few months later. Primary leiomyosarcoma of bone is a rare tumor, of which one of the most characteristic locations is the proximal third of the tibia. Magnetic resonance imaging with both T1- and T2-weighted sequences is essential to evaluate intramedullary and soft tissue tumor spread. To our knowledge, there are no characteristic signal patterns allowing to differentiate leiomyosarcoma from other primary malignancies of bone. Immunohistochemical and electron microscope studies are useful diagnostic tools.