Detection of t (14; 18) chromosomal translocation in paraffin-embedded tissues of follicular lymphoma and its clinical significance

Abstract

To study the genetic aberrations and their pathologic significance in follicular lymphoma (FL). Paraffin-embedded tissue samples of 55 cases of FL, 28 cases of other small B-cell lymphomas and 10 cases of reactive follicular hyperplasia were retrieved. Nested polymerase chain reaction (PCR) was used to detect clonal rearrangement of immunoglobulin heavy chain gene (IgH) in FL and other small B-cell lymphomas. The translocation t (14; 18) was studied by PCR and dual-color fluorescence in-situ hybridization (FISH) in FL. Cases of reactive follicular hyperplasia were used as controls. Amongst the 55 cases studied, 49 cases were nodal and 6 cases were extranodal. There were 33 males and 22 females. The male-to-female ratio was 1.5:1. The median age of the patients was 57 years. Twenty-five cases belonged to histologic grade 1, while 19 cases were grade 2 and 11 cases were grade 3. Beta-actin DNA was detected in 50 cases of FL. Amongst those 50 cases, clonal IgH rearrangement was present in 34 (68%). Twenty-four cases (48%) and 25 cases (50%) were positive for FR3A and FR2 respectively. Fifteen cases (30%) showed dual positivity for both FR3A and FR2. Thirty-four cases (68%) demonstrated clonal IgH rearrangement. As for other small B-cell lymphomas, 25 cases were positive for beta-actin. FR3A and FR2 were detected in 18 and 17 cases respectively. Clonal IgH rearrangement was demonstrated in 24 cases. In contrast, none of the 4 cases of reactive follicular hyperplasia showed the clonal rearrangement pattern. Amongst the 44 cases of nodal FL analyzed, t (14; 18) was detected in 15 cases (with 14 cases in MBR and 1 case in mcr). In general, FISH was superior to PCR in detecting t (14; 18) using paraffin-embedded tissue samples. The detection rate of clonal IgH rearrangement in FL is lower than that in other small B-cell lymphomas. Demonstration of t (14; 18) in paraffin-embedded tissue samples by FISH helps in diagnosis of FL. FISH is superior to PCR, as the technique is more sensitive and less labor intensive.