MUM1 expression dichotomises follicular lymphoma into predominantly, MUM1-negative low-grade and MUM1-positive high-grade subtypes.

We investigated the expression of MUM1 (multiple myeloma oncogene 1)/IRF4 (interferon regulatory factor 4) in 46 cases of follicular lymphoma (FL) and correlated this with grade and expression of CD10, Bcl-6 and Ki-67. The analysis suggests that MUM1 expression dichotomises FL into low-grade FL of CD10+/Bcl-6+/MUM1-/Ki-67low phenotype, and high-grade FL of CD10+/- /Bcl-6+/weak/MUM1+/ Ki-67high phenotype.