dup(12)(q13→qter) in two t(14;18)-negative follicular b-non-hodgkin's lymphomas

Two t(14;18)‐negative follicular B‐non‐Hodgkin's lymphomas with the same chromosomal abnormality, dup(12)(q13→qter), are presented. The absence of a BCL2 gene rearrangement was confirmed by molecular studies in both cases. Instead, duplication of a 12q segment was found. Further evidence for the presence of the dup(12)(q13→qter) was found using fluorescence in situ hybridization. dup(12q) may be equivalent to the trisomy 12 originally described in B‐chronic lymphocytic leukemia. This chromosome anomaly has also been reported in B‐non‐Hodgkin's lymphomas, usually in association with other chromosome anomalies and a more aggressive tumor phenotype. Occurrence of dup(12q) in two histologically similar cases of follicular small cleaved‐cell lymphoma without a typical t(14;18), suggests that this karyotypic change may play a critical role in some cases of follicle center‐cell lymphomas.