Morphological, immunohistochemical, and genetic features of 2 prototypical post-SOT mPTLD, BL (case p11), and DLBCL cases (case p10), respectively. Case p11: (A) hematoxylin and eosin, original magnification at ×400. (B) Tumor cells are diffusely positive for CD10 (immunostain, original magnification at ×400). (C) In situ hybridization for EBV RNA is positive in tumor cells (in situ hybridization, original magnification at ×400). (D-F) Neoplastic cells are negative for LMP1 (D), EBNA2 (E), and ZEBRA (F) immunostains, indicating latency pattern I (immunostains, original magnification at ×400). (G) FISH using MYC Break-Apart Probe (BAP) shows a signal constellation of 1 colocalized signal (yellow arrow) and 2 split signals (green and red arrows) in accordance with the gene rearrangement. Case p10: (H) DLBCL with focal plasmacytic differentiation (hematoxylin and eosin, original magnification at ×400). (I) Atypical cells are diffusely positive for MUM1 (immunostain, original magnification at ×400). (J-L) LMP1 (J), EBNA2 (K), and ZEBRA (L) immunostains show positive tumor cells, reflecting a pattern III of latency (immunostains, original magnification at ×400). (M-N) FISH using BAP for MYC (M) and IRF4 (N) genes show a normal pattern with 2 colocalizations in each nucleus for both hybridizations (yellow arrows).