Follicular lymphoma without t(14;18) and with BCL-6 rearrangement: a lymphoma subtype with distinct pathological, molecular and clinical characteristics.

ABSTRACT

Translocations involving the BCL-6 gene are frequently observed in diffuse large B cell lymphoma, but have rarely been reported in follicular lymphoma (FL). We studied a distinct cohort of FLs with a 3q27/BCL-6 gene rearrangement, but lacking the t(14;18) translocation. In 13/15 cases, translocations involved the 3q27 and the 14q32 regions. All cases displayed a marked follicular growth pattern and, in some instances, a monocytoid component. Tumor cells were CD5(-) CD20(+) CD23(-) CD43(-) BCL-6(+), and in the main CD10 negative (n = 10, 71%) and BCL-2 negative (n = 11, 78%). When compared to 20 typical t(14;18)(+) FLs, the presence of large follicles (P = 0.01) and a CD10(-)/BCL-2(-) phenotype were more frequently observed (P = 0.001) in our cohort. Clonal mutations arising in the BCL-6 first intron were observed in 5/7 cases with evidence of intraclonal heterogeneity, consistent with a germinal center origin. No significant difference was found in comparison to t(14;18)(+) FL regarding age, sex, performance status, bone marrow involvement or overall survival. However, in the 3q27(+) FL group, a stage III/IV disease and a bulky mass were less frequently observed. This study indicates that 3q27(+) FL without t(14;18) translocation have peculiar clinico-pathologic features and may correspond to a rare and distinct subtype of lymphoma originating from the germinal center.