Morphologic and IHC features of pediatric-type FL in adults. Representative example of a pediatric-type FL from an adult (cohort 2). The follicular proliferation is composed of variably sized follicles (A) with increased centroblasts, consistent with grade 3A (B). The follicles are composed of CD20+ B cells (C) that do not express BCL2 protein (D). (E, F) One patient with FL in cohort 2 had grade 3B histology. This lymphoma contained large, expansile follicles (E) composed of a uniform population of large centroblasts (F). Panels A, C, D, and E were captured at ×40 magnification; and B and F at ×400 magnification with the use of an Olympus, BX53 microscope, Olympus DP25 digital camera.