We report a 35-year-old male with leukemic change and gastric involvement of Burkitt's lymphoma. A monoclonal immunoglobulin (Ig), IgM-κ, was detected in the serum by means of immunoelectrophoresis. Immunophenotypical analysis showed that the neoplastic cells were CD20+, OKIal+, CD10-, CD21-, surface Ig+(M-κ), and cytoplasmic Ig-. The neoplastic cells did not secret Ig by using of protein A plaque forming cell assay. Active transcription of Ig hevy chain genes was not detected by cell dot analysis of the neoplastic cells. These findings support the possibility that the presence of the monoclonal Ig in the serum does not result from secretion of Ig from the neoplastic cells. The shedding of surface Ig from the neoplastic cells might result in the occurrence of monoclonal Ig in the serum.
