Double-hit follicular lymphoma with MYC and BCL2 translocations: a study of 7 cases with a review of literature.

Follicular lymphoma with MYC and BCL2 translocations, so-called double-hit follicular lymphoma (DH-FL), is rare. Here, we report the clinicopathological features of 7 cases of DH-FL. All neoplasms had a follicular pattern (1 partially diffuse). Five cases were predominantly low grade, 4 of which had focal (≤20%) grade 3A areas, and 2 cases were of grade 3. All cases were positive for pan-B-cell antigens, CD10, and BCL6; 6 cases were positive for BCL2. Ki-67 was less than or equal to 50% in 6 cases and 90% in 1 grade 3 case. Three patients presented with stage IV disease and 3 had a Follicular Lymphoma International Prognostic Index score of greater than 2. Six patients received immunochemotherapy, and 1 is still under induction therapy with rituximab, ibrutinib, and lenalidomide. Four achieved complete remission and two had a partial response with persistent or refractory disease. The median follow-up time was 25 months (range, 8.5-53.7 months). Two patients treated with standard regimen for follicular lymphoma had relapsed or refractory disease, and 1 died from complications of allogeneic stem cell transplant administered for relapse. In contrast, all 4 patients treated with more intensive regimen for double-hit lymphoma achieved complete remission. In summary, despite predominantly low-grade histology, cases of DH-FL in this study were aggressive and responded better to more intensive than standard treatment regimens, suggesting DH-FL is part of the spectrum of double-hit high-grade lymphoma.