Immunophenotypic and molecular analysis of a case of lymphocytic interstitial pneumonia.

A case of lymphocytic interstitial pneumonia was studied immunophenotypically and with molecular methods in order to clarify its lymphocytic clonality. The patient, a 43 year old Japanese female, underwent lobectomy for a suspected malignant lymphoma as no clear diagnosis could be made from the biopsy specimen. An ill-demarcated, yellowish and elastic firm lesion measuring 60 x 35 x 20 mm in size was located in the peripheral part of the middle lobe of the right lung. Histologically, the alveolar, peribronchial-vascular and subpleural interstitia within the lesion were thickened markedly with severe cellular infiltration largely composed of small lymphocytes with germinal centers. Immunostaining revealed immunoglobulin (Ig) kappa and Ig lambda-bearing cells to be evenly distributed, suggestive of polyspecificity. Immunoglobulin gene analysis further demonstrated the unrearranged germ-line DNA but no rearranged band. These results strongly indicated a reactive process rather than a neoplastic nature for the lesion.