Non-neoplastic pulmonary lymphoid proliferations

Abstract

Non-neoplastic pulmonary lymphoid proliferations encompass a spectrum of disease from small airway bronchiolar disease to diffuse interstitial disease. They include follicular bronchiolitis (FB), nodular lymphoid hyperplasia (NLH), and lymphocytic interstitial pneumonia (LIP). FB is characterized by the presence of hyperplastic lymphoid follicles with germinal centers, exquisitely bronchiolocentric. Patients with FB not uncommonly suffer from connective tissue disease such as rheumatoid arthritis or immunodeficiency. The differential diagnosis of FB includes other small airway diseases such as chronic bronchiolitis or constrictive bronchiolitis. In contrast, LIP is an interstitial lung disease with diffuse marked septal thickening by small lymphocytes, with admixed plasma cells and histiocytes. Patients with LIP often present with autoimmune disorders such as Sjögrens syndrome. Chronic hypersensitivity pneumonia and non-specific interstitial pneumonia enter the differential diagnosis of LIP. Patients with NLH are typically asymptomatic and present with solitary or multiple nodular infiltrates. The lung parenchyma is focally obliterated by a mass comprised of fibrosis admixed with a dense polymorphous lymphoid infiltrate, often with numerous germinal centers. By immunohistochemistry, the lymphoid infiltrate is predominantly CD3 + T-cells with CD20 + B-cells forming the germinal centers. The plasma cells and lymphocytes are polyclonal. NLH needs to be distinguished from low-grade lymphoma, mainly MALT lymphoma. Non-neoplastic pulmonary lymphoid proliferations encompass a spectrum of disease from small airway bronchiolar disease to diffuse interstitial disease. They include follicular bronchiolitis (FB), nodular lymphoid hyperplasia (NLH), and lymphocytic interstitial pneumonia (LIP). FB is characterized by the presence of hyperplastic lymphoid follicles with germinal centers, exquisitely bronchiolocentric. Patients with FB not uncommonly suffer from connective tissue disease such as rheumatoid arthritis or immunodeficiency. The differential diagnosis of FB includes other small airway diseases such as chronic bronchiolitis or constrictive bronchiolitis. In contrast, LIP is an interstitial lung disease with diffuse marked septal thickening by small lymphocytes, with admixed plasma cells and histiocytes. Patients with LIP often present with autoimmune disorders such as Sjögrens syndrome. Chronic hypersensitivity pneumonia and non-specific interstitial pneumonia enter the differential diagnosis of LIP. Patients with NLH are typically asymptomatic and present with solitary or multiple nodular infiltrates. The lung parenchyma is focally obliterated by a mass comprised of fibrosis admixed with a dense polymorphous lymphoid infiltrate, often with numerous germinal centers. By immunohistochemistry, the lymphoid infiltrate is predominantly CD3 + T-cells with CD20 + B-cells forming the germinal centers. The plasma cells and lymphocytes are polyclonal. NLH needs to be distinguished from low-grade lymphoma, mainly MALT lymphoma.