Lymphoid interstitial pneumonia.

ymphoid interstitial pneumonia (LIP) is one of a sedes of parenchymal pulmonary diseases discovered in the last few years. LIP has the histologic features of benign pseudolymphoma but it is more diffuse.' In LIP there is a predominance of mature lymphocytes in the interstitiurn of the lung which at times forms germinal centers. The process surrounds, but does not invade, structures normally present. A true lymphoma infiltrates the lung homogeneously, by surrounding and invading structures including larger bronchi and lymph nodes.2 The absence of involvement of local lymph nodes and of extrapulmonary tissues differentiates LIP from malignant lymphoma.14 Fourteen cases of histologically characteristic LIP have been rep0r ted . l~~ The etiology remains unknown. The clinical features of this disorder have not been clearly defined. Pulmonary function has not been previously described. This report presents the varying clinical, physiologic and immunologic features of LIP as demonstrated by three patients.