Southern blot analysis of IgH, BCL2, and BCL6 gene rearrangement. Tumor DNA samples from cases 35, 5, 152, 68, 27, 49, 44 (see Table 1) and 2 other lymphomas (lanes A and B) not included in the study were digested with BgIII and hybridized with probes for BCL2 (pSP64/18-4RH for MBR), J_H (pCm51/JH), and BCL6 (pGSc4.0 for the 3′ region of exon 1a of BCL6). All tumors except case 27 showed 1 or more rearranged JH bands, indicating sufficient tumor DNA. Case 27 showed 2 strong rearranged JH bands in both theHindIII and EcoRI digests (not shown), indicating that the BgIII digest was false-negative. Case 35 showed rearrangement for BCL2, and cases 68 and 44 showed rearrangements for BCL6. Comigration of 1 rearranged BCL2 and 1 rearranged JH band in case 35 indicates t(14;18). Case 152 did not show BCL6 rearrangement but had BCL6 rearrangement upon analysis with the pGSc4.0 probe in theHindIII digest, as well as F370 and F372 BCL6 probes in theBgIII digest and the F370 probe in the EcoRI digest. This indicates that the BCL6 breakpoint is present in the MTC of BCL6 (not shown).