Use of novel t(11;14) and t(14;18) dual-fusion fluorescence in situ hybridization probes in the differential diagnosis of lymphomas of small lymphocytes

Increasingly, molecular biologic techniques have become important in the di agnosis of non-Hodgkin lymphomas. In the differential diagnosis of lymphoma (s) of small lymphocytes (LSL), reliable detection of t(11:14) or t(14:18) would confirm the diagnosis of mantle cell lymphoma (MCL) or follicle cente r lymphoma (FCL), respectively. A total of 87 LSL cases (27 MCL, 39 FCL, 17 small lymphocytic lymphoma [SLL], 3 marginal zone lymphomas, and 1 paraimm unoblastic variant of SLL) were diagnosed by a combination of light microsc opy, immunohistochemistry, and flow cytometric immunophenotyping. Interphas e fluorescence in situ hybridization (FISH) for t(11:14) and t(14,18) using dual-fusion probes (Vysis. Downers Grove, IL) was performed on touch (n = 69) or gravity (n = 18) preparations from these cases. Of 27 MCL cases test ed, 25 (93%) had demonstrable t(11:14), none had t(14:18), and 2 were negat ive for t(11:14) and t(14:18). Twenty-five of 39 (64%) FCL cases had t(14,1 8), none had t(11:14), and the remaining FCL cases (14 cases [35%]) had nei ther t(11:14) nor t(14:18). All 17 (100%) SLL cases had neither t(11:14) no r t(14:18). All 3 (100%) marginal zone lymphoma cases had neither t(11:14) nor t(14:18). The case of paraimmunoblastic variant of SLL had t(11:14) and was negative for t(14;18). No discrepant [i.e., positive for both t(11:14) and t(14:18)] or false positive cases were noted. Interphase FISH using th ese commercially available probes is a useful adjunct to light microscopy, immunohistochemistry, and flow cytometric immunophenotyping in the diagnosi s of LSL. FISH can be performed successfully on archival single-cell prepar ations (touch preparations or gravity preparations) when fresh tissue is un available. No discordant or false-positive cases were identified.