Illustrative lymph node histopathology in APDS1. (A) Arrow is pointing toward the germinal centers identified by the presence of larger cells and numerous tangible body macrophages. (B) Circle defines the germinal centers with a rim of small lymphocytes with condensed chromatin (T cells). (C) CD3 and CD20 images showing out circle of monocytoid B cells (CD20). (D–E) Another feature that is often seen as marked plasmacytosis, like in this case with kappa greater than lambda (in tissue the ratio can be up to 4:1). ISH, in situ hybridization.