Delayed Diagnosis of Primary Pulmonary Sarcoma Arising from a Pulmonary Cyst in an Adult: A Case Report.

Primary pulmonary sarcoma is a rare disease and is much less common than lung cancer among tumors arising from pulmonary cysts. We report the case of a female patient who showed multifocal cysts in the left S9-10. Follow-up computed tomography (CT) revealed that the cyst tended to regress, but the solid component of the cyst wall continued to thicken, growing to a 10-cm-diameter tumor. Thoracoscopic left lower lobectomy was performed to diagnose and treat the cystic lung lesions. For the pathology of the pulmonary cystic lesion, it was marked by solid tumors composed of proliferative atypical spindle cells, with some trapped bronchial tissue. Based on the imaging and pathological findings, the diagnosis was primary pulmonary sarcoma arising from the pulmonary cyst. The present case highlights that, even when a pulmonary cyst appears to shrink, careful follow-up and timely surgical consideration are warranted if cyst wall thickening is observed.