[A case of surgically resected primary pulmonary lymphoma with IgG-paraproteinemia: gene analysis was effective for establishing its diagnosis].

A 69-year-old woman was hospitalized because of abnormal lung shadow and IgG-lambda paraproteinemia. She was otherwise healthy and asymptomatic. Chest roentgenogram showed a consolidation in the right lower lobe. Chest CT showed a tumour in S8 and subpleural interstitial shadow in S10. No intrathoracic lymphadenopathy was found. Serum IgG was 6,109 mg/dl. The cell count obtained by bronchoalveolar lavage (BAL) was 44.5% plasma cells and 17.5% lymphocytes. CD19-positive lymphocytes were prominent. The IgG/albumin ratio was 13 times higher, and IL-6/albumin ratio was 29 times higher in lavage fluid than in serum. Transbronchial lung biopsy (TBLB) specimen showed interstitial infiltration of plasma cells and lymphocytes. Right lower lobectomy was performed, and serum IgG subsequently decreased to about 4,000 mg/dl. DNA was extracted from the surgical specimen, and analyzed by Polymerase Chain Reaction (PCR) method. A rearrangement band was amplified with Fr3a & VLJH primers (immunoglobulin heavy chain gene). The infiltrated cells were proved to be monoclonal B-cells. This case was diagnosed as small lymphocytic lymphoma, plasmacytoid. Most primary pulmonary lymphomas are well differentiated B-cell type, and the histopathological findings resemble those of LIP or pseudolymphoma. Gene analysis may thus be an effective procedure for the distinction between inflammatory and neoplastic cell proliferation, such as LIP and lymphoma.