Richter transformation (RT) refers to the occurrence of an aggressive and treatment-resistant lymphoma that arises from the progression of chronic lymphocytic leukemia (CLL) and is associated with a poor prognosis. Disruptive mutations in the BCL6 co-repressor (Bcor) gene are found in up to 2% of CLL cases and often occur alongside Notch1 mutations, a common molecular alteration linked to RT. This co-occurrence points to a possible cooperative role in driving disease progression.