Variable heavy-chain gene analysis of follicular lymphomas: subclone selection rather than clonal evolution over time

To investigate B-cell receptor evolution in follicular lymphomas (FLs), imm unoglobulin variable heavy chain (VH) gene regions of 3 FLs were analyzed a t different time points. One FL with a high somatic mutation load and intra clonal VH gene diversity was investigated in situ, VH gene transcripts were amplified and sequenced from samples of approximately 50 tumor cells isola ted from frozen tissue sections by laser microdissection, Interestingly, th e mutation pattern of the prevalent subclone in the relapse biopsy was virt ually identical to that of a subclone isolated by microdissection from the presentation biopsy 9 years earlier. In a second FL, proof was obtained tha t the subclone that dominated the relapse sample had already been present i n the initial biopsy. The finding that subclones found in the relapses of t hese FLs had not evolved over time but were preexistent, challenges-the con cept of antigen-driven B-cell receptor evolution during disease course. (C) 2001 by The American Society of Hematology.