Does the proliferation fraction help identify mature B cell lymphomas with double- and triple-hit translocations?

Mationg-Kalaw E, Tan L H C, Tay K, Lim S T, Tang T, Lee Y Y L & Tan S Y ?(2012) Histopathology?Does the proliferation fraction help identify mature B cell lymphomas with double- and triple-hit translocations? Aims: The entity B cell lymphoma, unclassifiable, with features intermediate between diffuse large B cell lymphoma (DLBCL) and Burkitt lymphoma (BL) refers to B cell neoplasms that share overlapping characteristics of BL and DLBCL. A subset of these grey-zone lymphomas possesses C-MYC and IGH translocations but, in addition, contains additional rearrangements of BCL2 and/or BCL6 genes. The aim of this study was to investigate if the proliferation fraction by Ki67 immunostaining can be used to identify such double-/triple-hit lymphomas. Methods and results: We studied 492 cases of mature aggressive B cell neoplasms by histology, immunohistochemistry and interphase fluorescence in-situ hybridization (FISH) using break-apart probes against C-MYC, BCL2, BCL6, IGH, MALT1, PAX5 and CCND1. Forty Burkitt lymphomas and 28 cases of MYC+ double-/triple-hit lymphomas were identified. Of the latter, 77% and 54% displayed proliferation fractions exceeding 75% and 90%, respectively. With a cut-off of >75% by Ki67 immunostaining, the sensitivity and specificity for detection of MYC+ double/triple translocations was 0.77 and 0.36. Raising the proliferation fraction criterion to >90% improved the specificity to 0.62 at the expense of a low sensitivity of 0.54. Conclusions: Immunostaining for Ki67 is not a useful approach to prescreen B cell lymphomas for MYC+ double/triple translocations.