Hodgkin Lymphoma Variant of Richterís Transformation
Microscopically, sections from the splenic hilar lymph node show predominant involvement of CLL/SLL cells. In addition, some large pleomorphic cells resembling Hodgkin and Reed-Stemberg cells are noted scatteredly or in small clusters. The CLL/SLL cells are positive for CD79a, weak CD20 and CD5, and the large H-RS cells are positive for CD79a, CD20, CD30, CD15, EBV-LMP and weak PAX5.
Richter's syndrome occurs in 1-10% of patients with CLL/SLL, which denotes the development of high-grade non-Hodgkin lymphoma from CLL/SLL, mostly commonly diffuse large B-cell lymphoma and less commonly Hodgkin disease or acute leukemia. The high-grade lymphoma is usually clonally related to CLL/SLL, but can arise from a different progenitor clone due to sustained immunosuppression from treatment. Richter's syndrome may be triggered by viral infections, especially Epstein-Barr virus, and it is also associated with some chromosomal abnormalities and genetic defects.
Scattered RS cells may be present in CLL/SLL, but it should not be interpreted as Richter's transformation without a context of Hodgkin lymphoma background, i.e. mixed background of reactive lymphocytes, histiocytes and granulocytes.