A molecular analysis of biclonal follicular lymphoma: further evidence for bone marrow origin and clonal selection.

We report a follicular lymphoma (FL) case presenting the coexistence of two tumor cell subpopulations in lymph node (LN) and bone marrow (BM), which exhibited an inverse pattern of immunoglobulin light (IgL) chain gene rearrangement and expression: Igkappa-lambda+ in LN and Igkappa+lambda- in BM. These tumor clones shared an identical BCL2-IgH recombination, accompanying t(14;18)(q32;q21) translocation, and an identical variable, diversity and joining segments joining with clone-specific VH somatic hypermutations on the untranslocated IgH allele. Our study provides further evidence that FL clones, originating from common progenitor cells, can be developed independently at different sites and with different IgL expression after immune selection.