Primary osteosarcoma of the lung: report of a case.

Osteosarcoma of the lung without an extrathoracic primary tumor is extremely rare, with only eight cases documented in the literature, to the best of our knowledge. We report a case of primary osteosarcoma of the lung found in an asymptomatic 74-year-old woman. Computed tomography showed a heterogeneous mass beside the aortic arch, and the patient underwent a left upper lobectomy. The pathology results confirmed a diagnosis of primary osteosarcoma.