Introduction: Richter transformation (RT) represents an aggressive transformation of chronic lymphocytic leukemia (CLL), most commonly into diffuse large B cell lymphoma (DLBCL). It occurs in around 5% of patients with CLL.

Area covered: This review will focus on the biology and treatment of RT. We also address the management of RT in the era of targeted therapies. Based on clonal relationship of large cell component to CLL, 2 distinct subtypes could be identified: clonally-related RT which carries a worse outcome, and clonally-unrelated RT where the outcomes are similar to de novo DLBCL. Aberrations of TP53, CDKN2A, MYC, and NOTCH1 are common in RT, many of which are acquired at the time of transformation. PET scan remains the imaging modality of choice for patients with suspected RT. It is important to perform a biopsy rather than fine needle aspiration (FNA) of the suspicious lesions, as FNA can lead to false negative results. Chemoimmunotherapy remains the treatment of choice, though the outcomes remain suboptimal. The median survival is less than 1 year. Novel therapies are needed for patients with RT.

Expert commentary: RT remains an unmet medical need; the role of targeted therapies, including immunotherapy needs to be explored.