Differential expression of TCL1 between t(14;18)–negative and BCL2-negative (FL--) and t(14;18)–positive FLs (FL+) as detected by immunohistochemistry. (A) TCL1 is absent in 80% of t(14;18)–negative FLs without BCL2 expression, whereas it is present in 84% of t(14;18)–positive FLs as shown by immunohistochemistry (P < .0001, Fisher Exact). (B) Representative stainings for TCL1 in FL+ and FL--. (C) “Composite” FL with BCL2-positive (white arrows) and BCL2-negative/BCL2-weak (black arrowheads) atypical follicles. Atypical follicles with BCL2 expression stain positive for TCL1, whereas in BCL2-negative follicles TCL1 expression is absent. Of note, BCL2-negative atypical follicles showed decreased CD10 expression and elevated proliferation (Ki67) compared with BCL2-positive atypical follicles. Images were captured using a Olympus, Color View, BX50 microscope, the Color View digital camera, and the analysis work soft imaging system (all Olympus).