Double hit lymphoma: How do we define it and how do we treat it?

Double/triple hit lymphoma is recognised as a distinct entity within the heterogeneous group of high grade B-cell lymphomas, accounting for between 5 and 10% of cases of diffuse large B-cell lymphoma. Under the WHO 2016 it is now known as high-grade B-cell lymphoma with rearrangements of MYC and BCL2 and/or BCL6. When treated with standard chemotherapy it has a poor outcome. There is currently no standard of care for the management of this condition. Diagnosing double hit lymphoma requires identification of translocations of MYC and BCL2 and/or BCL6. This review will discuss the role of stratification to screen cases based on immunohistochemical profiling as a viable option. Treatment options in the frontline and relapsed setting will be reviewed based on the current literature. Recognition of the risk of CNS involvement and how best to manage this will be discussed. Future considerations and current research will be described.