[A case of primary pulmonary B cell lymphoma confirmed by gene analysis]

A 76-year-old man visited our clinic with chest radiographic evidence of a coin lesion in the right middle lung. Chest CT demonstrated an infiltrative shadow mainly in the S4 segment. Lymphoproliferative disorders were suggested by transbronchial lung biopsy. Middle lobectomy was performed. Pathological study showed massive proliferation of mature lymphocytes. Immunoperoxidase studies could not demonstrate a neoplastic monoclonal process. Pseudolymphoma was diagnosed. High molecular weight DNAs were extracted from frozen specimens. Whether genes of immunoglobulins and T-cell receptors were rearranged was investigated using DNA probes against JH and TCR beta-1 receptor gene. One rearranged band was found in the JH chain. No rearranged band appeared in TCR beta-1 chain. B cell lymphoma was diagnosed instead of pseudolymphoma.