Lymphocytic interstitial pneumonitis

A representative field of a lung biopsy specimen from a child with lymphocytic interstitial pneumonitis (LIP), demonstrating a diffuse infiltrate of mature and immature lymphocytes, plasma cells, and histiocytes in the alveolar septae and pulmonary interstitium. Nodular formation of lymphocytes is also seen. Although fibrosis is not a typical feature, widening of the pleura with fibrous tissue is seen.