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The value of gene analysis was assessed in patients with pulmonary pseudolymphoma. Two patients with histopathologic evidence of pseudolymphoma took part in the study. High molecular weight DNA was extracted from resected specimens and digested with restriction enzymes, followed by southern blotting. Gene rearrangement of immunoglobulins and T-cell receptors was investigated using DNA probes against heavy chain (H chain), kappa chain, and lambda chain of immunoglobulin genes and that against the beta-chain of T-cell receptor genes. Both patients with pseudolymphoma showed rearranged bands for the H chain; B-cell lymphoma was diagnosed from the gene analysis. Gene analysis is a valuable method when it is difficult to judge whether the tumor cells are of T-cell origin or B-cell origin in phenotype analysis by immunohistologic studies and when it should be judged whether or not the lymphoid hyperplasia is tumor related.

The authors performed gene analysis of pulmonary lymphoproliferative disorders. Cell suspensions were obtained from tissues of malignant lymphoma or pseudolymphoma in Cases 1 to 3. High-molecular-weight DNA was extracted from these specimens, digested with restriction endonucleases, size-fractionated by agarose-gel electrophoresis and transferred by the Southern procedure to nitrocellulose. Hybridization to nick-translated 32P DNA probes of the immunoglobulin JH, C kappa, C lambda, regions, and T cell receptor beta 1 region. In case 1 and 2, which were diagnosed as B cell lymphoma, cells from tumor had rearranged heavy chain genes, clearly establishing the clonal nature. In Case 3, which was diagnosed as pseudolymphoma, the tumor contained clonal immunoglobulin gene rearrangements as detected with both the JH heavy chain and C kappa light chain gene probes. It was concluded that gene analysis is an effective procedure for establishing a diagnosis of lymphoma in neoplastic disorders of uncertain cell type and for detecting clonal T cell or B cell populations with atypical lymphofollicular hyperplasia.