[A case of primary pulmonary lymphoma associated with Sjögren syndrome and IgM monoclonal gammopathy confirmed by DNA rearrangement].

A 70-year-old man was admitted for evaluation of an abnormal shadow on his chest X-ray film, consisting of a mass containing an air bronchogram. He was also found to have a monoclonal gammopathy (IgM kappa type) and Sjögren syndrome. Open lung biopsy was performed with the suspicion of primary pulmonary lymphoma or pseudolymphoma. Southern blot analysis of the tissue revealed clonal rearrangements of immunoglobulin gene, supporting the diagnosis of B-cell lymphoma. Using conventional immunoperoxidase staining (PAP) method, the monoclonality in the tissue specimen is sometimes quite difficult to prove. Southern blot analysis, however, gives more accurate and reliable results. The analysis of immunoglobulin gene rearrangements is quite useful in determining the presence or absence of monoclonality in a specimen in cases of suspected lymphoproliferative disease such as primary pulmonary lymphoma and pseudolymphoma. We strongly recommend the use of Southern blot analysis in making the diagnosis of lymphoproliferative disease.