Chronic follicular pleuritis: a B cell-rich form of nonspecific pleuritis/fibrosis

The parietal pleura is often biopsied in patients with idiopathic pleural effusion, and in up to 40% of cases, a diagnosis of nonspecific pleuritis/fibrosis (NSP) is rendered. The histology of this reaction has not been well described including a pattern of B cell lymphoid hyperplasia described as "chronic follicular pleuritis (CFP)". Thirty-two cases of NSP were studied, of which 13 (41%) corresponded to CFP with the remainder displaying a fibrinous and organizing pleuritis with varying degrees of collagenization. CFP had similar etiologies as NSP with long term follow-up, including cardiac disease, pericarditis, asbestos exposure, and occult malignancy. The importance of recognizing a previously undescribed B cell/plasma cell pleural inflammatory response in reactive pleural disease is discussed.