Cytologic perspectives on neoteric B-cell lymphoproliferative disorders

High performance of multiplex fluorescence in situ hybridization to simultaneous detection of BCL2 and BCL6 rearrangements: useful application in the characterization of DLBCLs

Chromosomal rearrangements involving BCL2, BCL6 and MYC are commonly found in the most frequent B cell lymphomas, namely follicular lymphomas (FLs) and diffuse large B-cell lymphomas (DLBCLs). Particularly, BCL2-rearrangement represents a diagnostic hallmark in FLs, whereas MYC translocation can occur simultaneously with BCL2 and/or BCL6 rearrangements, defining a specific category of DLBCLs with a poorer prognosis. In this study, we aim to validate the diagnostic performance of multiplex BCL2/BCL6 FISH approach in formalin-fixed paraffin-embedded FLs and DBCLs and cytological samples of DLBCL comparing to the classic set of single break-apart probes. We collected a series of lymphomas, including 85 DLBCLs, 45 FLs and 36 other B-cell lymphoma histotypes and 16 cytological samples of DLBCLs. MYC, BCL2 and BCL6 rearrangements were previously assessed by a classic FISH test using single break-apart probes. All samples were analysed by a multiplex FISH assay. In the FL series, 38 cases showed BCL2-R; in the DLBCLs series, MYC-R was detected in 21 out of 85 DLBCL patients, BCL2-R in 10 out of 85 and BCL6-R in 33 out of 85. In the DLBCL cytological series, MYC-R was detected in 4 out of 16, BCL2-R in 4 out of 16 and BCL6-R in 1 out of 16. Notably, in FFPE, 13 double-hit lymphomas (DHLs) and 3 triple-hit lymphomas (THLs) were detected; in the cytological series, only 3 DHL cases were observed. The dual BCL2/BCL6 FISH probe test results were fully concordant with the results obtained using classic BCL2 and BCL6 single break apart. Particularly, multiplex FISH to simultaneously detect BCL2-R and BCL6-R on a single slide could find a wide application in the characterisation of double- and triple-hit DLBCLs.

"Triple hit" lymphomas: A retrospective cytology case series of an uncommon high grade B-cell malignancy with C-MYC, BCL-2 and BCL-6 rearrangements

The Revised fourth Edition World Health Organization (WHO) Classification of Tumors of Hematopoietic and Lymphoid Tissues suggests novel categories, including "high grade B-cell lymphoma with MYC and BCL2 and BCL6 gene rearrangements." These diseases are known colloquially as "double hit" and "triple hit" lymphomas. The "first-hit" in these cases is the harboring of a MYC rearrangement. Concurrent derangements of BCL2 and BCL6 can be the "second-hit" or "third-hit." To our knowledge, this is the first report of "triple-hit" lymphomas in cytology specimens. The files of the Cleveland Clinic (January 2007 through December 2017) were searched for all "triple hit" lymphomas. Four cases met inclusion criteria (cytology slides in files and histologically confirmed "triple hit" lymphoma). All slides were reviewed. The mean age was 65 years, with a male predominance. All patients presented at advanced stage and showed progressive disease despite therapy. FISH studies (histologic sections) confirmed translocations of MYC (8q24), BCL2 (18q21) and BCL6 (3q27) in all patients. All cases were characterized by high cellularity, dispersed cells, presence of stripped nuclei, lymphoglandular bodies, apoptotic bodies, cytomegaly, nucleomegaly, nuclear envelope irregularities, macronucleoli (most often single), recognizable mitoses and presence of cytoplasmic vacuoles (variable). The WHO recommends that all large B-cell lymphomas be investigated using cytogenetic or molecular techniques. Concurrent inhibition of MYC and BCL2 is a potentially effective treatment strategy for triple hit lymphomas, and an expanding literature exists regarding predictive biomarkers and therapeutic regimens. It is our intention to raise awareness of this uncommon mature B-cell neoplasm within the cytodiagnostic community.