Multi-institutional retrospective cohort study of spontaneous pneumothorax.

Spontaneous pneumothorax (SP) affects only a subset of patients in a variety of disorders. This multi-institutional study attempted to identify unique clinicopathologic features of spontaneous pneumothorax (SP) in a large cohort. A total of 111 cases from 109 patients were retrieved from 3 institutions over an 11-year period: 27 women, 82 men. 66 were smokers, 16 were non-smokers, 27 unknown. Sixty-six cases (61%) had identifiable disorders (secondary SP). Seven patients had a family history of lung disease: 2 of pneumothorax, 2 of lung cancer, and 1 each of emphysema, COPD, and not further classified. Forty-three cases (32 men, 11 women) were primary. The average age was 28 (men) and 37 (women). 17 smoked, 14 were non-smokers, and 12 unknown. In 26%, a unique recently described entity, pneumothorax-associated fibroblastic lesion (PAFL), was noted. 16% of this subset also had cellular alveolar septae. Abundant intraalveolar macrophages were noted in 12 cases. Five cases of unknown etiology had extensive bullous lung disease not otherwise classified. One patient had unusual cellular areas suggestive of LAM but negative for HMB-45. In conclusion, several distinct morphologic lesions were identified: PAFL, a subset with cellular septae, and a third with numerous intraalveolar macrophages.