Pleuropulmonary synovial sarcoma is a rare malignancy that often presents like any other thoracic tumor with symptoms such as chest pain or cough. Here we describe 4 young adults who underwent surgery for apparently benign recurrent pneumothoraces and who, unexpectedly, were found upon histologic and molecular examination of the resection specimen to have cystic primary pleuropulmonary synovial sarcoma. These cases highlight (a) the importance of cytogenetic analysis in making the diagnosis, as confusion with other spindle cell sarcomas or cystic neoplasms can occur and (b) the importance of thorough examination of all resected tissue in cases of recurrent pneumothorax.