[Hodgkin's disease variant of Richter's syndrome. Two cases and literature review].

We report the clinical and immunohistological features of two cases of chronic lymphocytic leukaemia (CLL) with Hodgkin's transformation. These cases occurred in a 70-year-old man with a three-year history of CLL and in a 76-year-old man with a few months history of CLL. Microscopic examination showed the presence of large tumor cells with the morphological and immunophenotypic features of classical Hodgkin and Reed-Sternberg (R-S) cells, in a background of otherwise typical B-CLL. The transformation of CLL into large B cell lymphoma (Richter's syndrome) is a well-documented phenomenon. Only rarely does CLL transform into Hodgkin's lymphoma, but this diagnosis is often easy and offers few differential diagnoses. The major points of interest lie in the pathogenetic relationship between CLL and Hodgkin's disease, and in the potential clinical implications of this peculiar condition. Literature on the subject indicates that identical IgH gene rearrangements in micromanipulated R-S and CLL cells have been identified in 7/12 cases. In these patients, the R-S and CLL cells belong to the same clonal population, suggesting a progression from the underlying CLL cells. This group appears to have a poor prognosis, identical to classical Richter's syndrome. In other cases, the R-S cells were often Epstein-Barr virus (EBV) positive and did not share the clonal rearrangements identified in CLL cells, suggesting that Hodgkin's disease in these patients could represent a second malignancy, EBV-related and favored by immunosuppression, associated with a better prognosis.