Rare lung sarcoma causing repeated collapsed lungs

What happened, in summary

A woman in her 60s who had never smoked developed a spontaneous collapse of her left lung. A chest tube relieved the problem, and CT showed what appeared to be a benign subpleural air space or a loculated pneumothorax with mild nodularity. The plan was repeat imaging in 1 year.

About a year later, she returned with shortness of breath and chest pain and was found to have another left-sided pneumothorax. A second chest tube again resolved her symptoms. CT did not show a clear mass, only a small bleb in the left lower lobe. Because the recurrent pneumothorax was attributed to that bleb, she underwent video-assisted thoracoscopic wedge resection and mechanical pleurodesis.

The surgical pathology unexpectedly revealed biphasic synovial sarcoma arising in the lung. The tumour was positive for CD99, epithelial membrane antigen, TLE1 and BCL-2. Molecular testing detected an SS18-SSX2 fusion, confirming primary pleuropulmonary synovial sarcoma. The wedge-resection margin contained tumour, but PET imaging showed no metastatic disease. The cancer was classified as Stage I.

She therefore returned for definitive surgery with a left-lower lobectomy and pleural adhesiolysis. A level 11 lymph node was removed and was negative for cancer. Because the tumour was low grade and confined to the lung, she did not receive chemotherapy or radiation.

Follow-up visits showed continued recovery, and surveillance imaging at 3 years found no evidence of disease. Her diagnosis was made only after surgery for the second pneumothorax, because CT had not shown a typical lung mass.