Bronchoalveolar lavage in primary pulmonary lymphoma with monoclonal gammopathy.

We performed bronchoalveolar lavage in a patient with pulmonary lymphoma and IgM lambda monoclonal serum gammopathy previously not diagnosed accurately by histologic examination and not treated for 5 yr after detection of a pulmonary infiltrate. The infiltrate increased slowly in size accompanied by coughing and sputum and a gradual increase in serum IgM throughout the 5-yr period. High IgM in the lavage fluid was noted with an IgM/albumin ratio 4.8 times higher in the lavage fluid than in the serum. Protein immunoelectrophoresis of the lavage fluid was identical to that of the serum. A primary pulmonary lymphoma was diagnosed on the basis of findings in the lavage fluid. The patient showed decreased serum IgM and marked improvement of the infiltrate by chemotherapy and radiation. Thus, bronchoalveolar lavage, including analysis of the proteins in lavage fluids, appears to be a simple and useful method for diagnosing primary pulmonary lymphomas.