Richter transformation

Richter transformation (RT) represents a clonal evolution event in which CLL/SLL transforms into a more aggressive malignancy, typically DLBCL (~90% of cases), though Hodgkin lymphoma transformation can also occur. Pathophysiologically, most cases are clonally related to the original CLL clone, arising from additional genetic alterations including TP53 mutations/deletions, NOTCH1 mutations, MYC activation, and loss of CDKN2A. A minority of cases are clonally unrelated, representing de novo DLBCL. Clinically, patients present with rapid lymph node enlargement (often asymmetric), B symptoms (fever, night sweats, weight loss), elevated LDH, and rapidly rising lactate dehydrogenase levels; extranodal involvement is common. Diagnosis requires biopsy (PET-CT guided to identify the most metabolically active site, as SUV >5 suggests transformation) showing large cell morphology distinct from the underlying CLL. Risk factors include unmutated IGHV status, NOTCH1 mutations, trisomy 12, and prior fludarabine-based therapy. Prognosis is poor, with median overall survival of 8-12 months; treatment typically involves anthracycline-based chemoimmunotherapy (e.g., R-CHOP) similar to de novo DLBCL, though response rates are lower in clonally related cases. Allogeneic stem cell transplant may be considered in eligible patients achieving remission. This is a high-yield concept for Step 2 as it tests understanding of malignant transformation, the importance of recognizing red flags (rapid clinical deterioration) in a patient with known CLL, and the need for tissue biopsy confirmation.