In each case the transformed lymphoma possessed an identical pattern of immunoglobulin heavy chain and/or BCL2 rearrangement to the corresponding original low-grade B-cell lymphoma, confirming their identity as transformed B-cell lymphoma.
High levels of bcl-2 expression were observed in both the follicular and transformed lymphomas, whereas the expression of c-myc was low in the follicular lymphoma and increased in the transformed lymphoma.
All patients from Group A showed IHC positive reaction on FCL remnant (small cleaved cells) but only 2 (18%) were positive in DLBCL areas, suggesting either the loss of the bcl-2 expression on the transformed lymphoma, or, alternatively, the development of a second disease when the first lymphoma transforms.
All 18 pretransformation follicular lymphoma specimens displayed at least one immunoglobulin gene and BCL-2 rearrangement in common with the corresponding histologically progressed lymphoma, indicating a clonal relationship between the original follicular lymphoma and the histologically transformed lymphoma.