Leiomyosarcomas are cancers of smooth muscle cells that can arise from any location but occur most often in the uterus, retroperitoneum, or intraabdominal region. Primary leiomyosarcomas of the lung are extremely rare and are often diagnosed as a mass on routine chest radiography. Metastasis is uncommon and typically occurs late in the disease process, indicating the importance of early detection. Surgical excision is generally curative, offering patients optimal prognoses. The authors describe a 56-year-old asymptomatic man who was found to have a pulmonary mass on routine chest radiography. Further testing revealed a primary pulmonary leiomyosarcoma. The tumor was excised and postoperative osteopathic manipulative treatment was applied to help facilitate patient recovery. A brief discussion of the typical clinical presentation, prevalence, and medical management of these tumors is included.