Double-hit lymphoma is defined by actual structural changes in the chromosomes (gene translocations).
Double-expressor lymphoma is defined by an overabundance of certain proteins, but without those specific chromosomal rearrangements.
Both indicate aggressive types of non-Hodgkin lymphoma and require specialized treatment.
Double-Hit Lymphoma (DHL)
Occurs when there are specific structural rearrangements (translocations) of the MYC gene along with BCL2 and/or BCL6 genes.
Diagnosis: Identified using genetic tests like fluorescence in situ hybridization (FISH) to pinpoint chromosome changes.
Behavior & Prognosis: Highly aggressive, fast-growing, and historically associated with a poor response to standard chemotherapy (like R-CHOP).
Double-Expressor Lymphoma (DEL)
Occurs when lymphoma cells produce unusually high amounts of both MYC and BCL2 (or BCL6) proteins, but without the underlying chromosomal translocations found in DHL.
Diagnosis: Identified using immunohistochemistry (a staining method on tissue biopsies to check protein levels).
Generally more aggressive than standard diffuse large B-cell lymphoma (DLBCL), though survival outcomes often differ from and can be slightly better than the genetic changes seen in DHL.
Understanding whether a lymphoma is driven by genetic translocations (Double-Hit) versus protein overexpression (Double-Expressor) is important, as oncologists use this information to determine the most effective treatment strategies.