Figure 4. Richter transformation to classic Hodgkin lymphoma: (A) Low-power H&E-stained image showing the periportal area (blue oval) infiltrated by inflammatory cells and histiocytes causing granuloma, with adjacent area (red oval) showing the large, atypical cells infiltrating the liver parenchyma. (B) High-power H&E-stained image showing the large atypical binucleated to multinucleated Reed-Sternberg cells (arrow). (C) RS cells with no reactivity to ALK immunostaining (arrow). (D) RS cells (long arrow) with weak reactivity for Pax-5 but diffuse reactivity for background clonal/CLL-specific B cells (arrowhead). (E, F) The intense reactivity for CD 30 and CD 15 by RS (arrows) confirms the CLL transformation to CHL, respectively. (G) The background CLL cells showed weak CD 20 reactivity (arrow) and negative activity in RS cells (arrowhead). (H) Both RS cells (arrow) and CLL B cells (arrowhead) showed positive Bcl-2 reactivity and (I) positive reactivity for Eber-ISH was seen only in RS cells (arrow).