Double – hit (DH) lymphomas are a recently discovered subtype of lymphoma that is defined by a chromosomal breakpoint affecting the MYC/8q24 locus in combination with another recurrent breakpoint, for instance a t(14;18)(q32;q21), involving BCL2. In the 2008 WHO classification, they are classified as “B cell lymphoma unclassifiable with features intermediate between Diffuse Large Cell Lymphoma(DLBCL) and Brkitt’s Lymphoma(BL)”. Thus, it is somewhere between intermediate and highly aggressive lymphomas in how it behaves.
In some ways it is similar to Burkitt’s; however, while the diagnosis of Burkitt lymphoma (BL) is generally straightforward, these lymphomas tend to have atypical morphologic and/or immunophenotypic features that overlap with other types of high-grade B-cell lymphoma, particularly diffuse large B-cell lymphoma (DLBCL). They often have an extremely poor prognosis, with a median survival of 6 or so months and represent an entity distinct from both Burkitt’s Lymphoma and DLBCL.
Unfortunately, it is no known how to treat double-hit lymphomas. The prevailing paradigm among oncologists has been to treat more aggressive cancer more aggressively but it is now being questioned. While it is tempting after initial chemotherapy to consolidate with high dose therapy and transplantation, the entity is too new to have accumulated significant published information on response to therapy and role of transplantation. NCCN currently recommends for DLBCL: ”consider high dose therapy Category 2B for complete and incomplete responders in high risk patients”. That seems to be a reasonable approach also to a Double Hit Lymphoma at this time.
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