Multiple brain tumors of diffuse large B cell lymphoma in a patient with lymphoplasmacytic lymphoma: PCR and DNA sequence analysis show evidence show evidence of differences in clonality of two B cell malignancies

Multiple brain tumors of diffuse large B cell lymphoma (DLBL) were observed in a 75-year-old man with Waldenstrom's macroglobulinemia (WM). Paravertebral and multiple subcutaneous nodules occurred in succession and he died 4 months after onset. We investigated B cell monoclonality by means of polymerase chain reaction (PCR) analysis and sequencing of the immunoglobulin heavy chain of paraffin-embedded sections. The PCR product of the brain tumors showed a different rearrangement pattern from those of the other sections. The co-occurrence of DLBL with WM is rare, and some investigators have examined the clonality of the two malignancies. This case is important because DLBL brain tumors co-occurred with WM, enabling us to prove that DLBL and WM have different clonality.