Pulmonary Relapse of Osteosarcoma Following Presentation With a Pneumomediastinum and Localized Disease at Diagnosis.

Pneumothorax is a well-described complication of osteosarcoma. Conversely, the presence of a pneumomediastinum to our knowledge has been reported just once in a patient with osteosarcoma, and never without detectable lung metastasis. We report the case of an 18-year-old male with a localized, distal femur osteosarcoma who was found to have an asymptomatic pneumomediastinum and pneumatocele at diagnosis, and then 16 months later experienced a pulmonary relapse. Our case suggests that these findings may represent the presence of occult metastatic disease and cautions providers to treat appropriately and provide surveillance with a high index of suspicion for pulmonary recurrence.