REACTIVE PULMONARY LYMPHOID DISORDERS

The two main reactive pulmonary lymphoid disorders are lymphoid inters titial pneumonia and follicular bronchitis: bronchiolitis, both pathol ogical entities with a variety of aetiologies. We reviewed the morphol ogical and immunohistochemical features of 26 cases with one or other of these two diagnoses, to explore the possibility that they represent ed overlapping patterns of hyperplasia of the bronchopulmonary immune system. The polymerase chain reaction was used to determine the clonal ity of the infiltrates, Histologically, there was a spectrum of change s with two main components, An interstitial infiltrate of mainly T lym phocytes, plasma cells and histiocytes predominated in lymphoid inters titial pneumonia, whilst lymphoid follicles predominated around airway s in follicular bronchitis/bronchiolitis. Classification of the disord er rested on which component the pathologists believed to be dominant, In two cases, histology and immunohistochemistry suggested lymphoma, and in one of these cases this diagnosis was confirmed by the polymera se chain reaction, One case of lymphoid interstitial pneumonia produce d three bands, The remainder produced polyclonal patterns when samples were adequate, Clinically, there was no clear difference between pati ents with the two disorders, or patients with pathological features of both.