The gene located at chromosome 18 band q21 is rearranged in uncultured diffuse lymphomas as well as follicular lymphomas.

The karyotypic abnormality t(14;18)(q32;q21) is reported to occur in 75% of follicular lymphomas. This translocation results in the rearrangement of a putative oncogene bcl-2, which resides at chromosome 18 band q21 (the 18q21 gene). Using two human genomic DNA fragments cloned from the chromosome 18 band q21 as probes, we analyzed 65 uncultured human lymphoma samples by the Southern blot technique. The 18q21 gene was rearranged in 18 of 26 (69%) follicular lymphomas, 3 of 5 (60%) follicular lymphomas transformed to large cell lymphomas, 8 of 20 (40%) diffuse large cell lymphomas (DLCLs), and 2 of 7 (29%) small noncleaved cell lymphomas (SNCs). Our analysis detected rearrangement of the 18q21 gene in 10 of 13 (77%) cases in which the t(14;18)(q32;q21) translocation was found by cytogenetic techniques. Our analysis also proved helpful in difficult karyotyping situations: (a) identifying the donor chromosome fragment as chromosome 18 band q21 in 4 of 9 (44%) cases that cytogenetically displayed a 14q+ chromosome of unknown origin, and (b) identifying a rearrangement of chromosome 18 band q21 in 12 of 18 (67%) cases that cytogenetically yielded no cells in metaphase. We also demonstrated three cases of submicroscopic rearrangement of the 18q21 gene. In our studies, patients with DLCLs and rearrangement of the 18q21 gene had a significantly higher incidence of extranodal involvement when compared with patients with DLCLs and no 18q21 gene rearrangement (P = 0.03).