Transformation of follicular lymphoma (FL) into high-grade B-cell non-Hodgkin lymphoma, usually diffuse large B-cell lymphoma (DLBCL), occurs in 25–35% of patients.1 This transformation has been shown to occur as a result of gain of MYC (8q24) rearrangement in addition to the t(14;18)(q32;q21), leading to a ‘double-hit’ lymphoma.2–10 Indeed, 5% of all FL with a BCL2 breakpoint will acquire a MYC rearrangement during the course of the disease.2 Double-hit lymphomas with MYC and BCL2 rearrangements have overexpression of BCL2 (a potent anti-apoptotic protein) and MYC (an enhancer of cell proliferation), leading to rapid cell accumulation.2 ,8 ,10 The MYC rearrangement in double-hit lymphoma has an IG light chain or a non-IG partner gene more commonly than in classical Burkitt lymphoma (BL) (49% vs 18%).2 ,11 Double-hit lymphomas comprise a substantial proportion of cases in the ‘B cell lymphoma, unclassifiable, with features intermediate between DLBCL and BL’ category described in the 2008 revision of the WHO classification of lymphomas.1

Several studies have been based on the hypothesis that the t(14;18)(q32;q21), resulting in IGH–BCL2 rearrangement, occurs as the primary event in double-hit lymphomas and that these lymphomas remain subclinical or low grade until acquisition of MYC rearrangement. At that point, the neoplasm transforms to a high-grade lymphoma with associated clinical presentation.2 ,5 ,10 ,11 High-grade lymphoma co-existing with low-grade FL within a single tumour has been reported previously,6 ,7 but cytogenetic evidence of concurrent low- and high-grade components has been demonstrated only in rare cases.12 ,13

We report a case of non-Hodgkin lymphoma (NHL) containing low grade and two immunophenotypically and genetically distinct high-grade elements within the same lymph node. The pattern of genetic abnormalities detected in …