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

Summary 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)”. 32 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 followup, 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.