Analysis of the immunoglobulin heavy chain gene of secondary diffuse largeB-cell lymphoma that subsequently developed in four cases with B-cell chronic lymphocytic leukemia or lymphoplasmacytoid lymphoma (Richter syndrome)

The immunoglobulin heavy chain gene (IgH gene) was analysed in four cases o f B-cell Richter syndrome, in order to determine whether a secondary diffus e large B-cell lymphoma (DLBCL) could arise from the same clone as the init ial B-cell chronic lymphocytic leukemia (B-CLL) and lymphoplasmacytoid lymp homa (LPL) or be a de novo event, and whether secondary DLBCL shows an intr aclonal microheterogeneity. Both the initial B-CLL and secondary DLBCL in t wo cases expressed CD5 antigen. Both samples of the initial B-CLL or LPL an d the secondary DLBCL in three cases were examined for comparison. The poly merase chain reaction-amplified IgH gene of secondary DLBCL in two cases (C D5(+) case and CD5(-) case) were different from those of the initial B-CLL, revealing a new malignant clone. The other case (CD5(-)) showed that secon dary DLBCL had a sequence identical to the initial LPL, indicating the same clonal origin. The variable region of the IgH gene of secondary DLBCL (CD5 (+) two cases and CD5(-) two cases) exhibited a 0.5-9.0% somatic mutation r ange and no intraclonal microheterogeneity.