Molecular cytogenetic evidence of t(14;18)(IGH;BCL2) in a substantial proportion of primary cutaneous follicle center lymphomas.

In contrast to nodal follicular lymphoma, limited data exist on genetic changes in primary cutaneous follicular lymphoma (primary cutaneous follicle center lymphoma according to WHO-EORTC). The detection rate of the BCL2 rearrangement, representing the characteristic t(14;18)(q32;q21) underlying follicular lymphoma, by polymerase chain reaction (PCR) has been reported to vary over a wide range (0%-41%), and only a few cases have been studied by molecular cytogenetic techniques such as fluorescence in situ hybridization (FISH). In this study, 27 primary cutaneous follicle center lymphomas were analyzed by FISH and the results compared with those obtained by PCR. FISH demonstrated translocations affecting the immunoglobulin heavy chain locus (IGH) in 14 of 27 cases (52%): a t(14;18)(q32;q21) involving BCL2 was found in 11 cases (41%), a t(3;14)(q27;q32) affecting BCL6 in 2 cases (7%), and in 1 case the partner gene of IGH could not be identified. Interestingly, PCR did not detect BCL2 rearrangement in any case. These data suggest that the t(14;18)(q32;q21) frequently occurs in primary cutaneous follicular lymphoma. The reason(s) why BCL2 rearrangements escape the detection by PCR is (are) not clear but could be due to BCL2 mutations, breakpoints outside the amplified DNA, or a high load of somatic mutations.