BACKGROUND.
Mantle cell lymphoma can be difficult to differentiate cytologically from other small cell non-Hodgkin lymphomas. Nevertheless, the distinction is important, because mantle cell lymphoma is more aggressive than other small cell non-Hodgkin lymphomas. The purpose of this study was to determine whether fluorescence in situ hybridization (FISH) is helpful in diagnosing mantle cell lymphoma on fine-needle aspiration (FNA) specimens by detecting the t(11; 14)(q13;q32) translocation that is characteristic of this tumor.
METHODS.
Fifty-five lymph node FNA specimens from 53 patients were analyzed using FISH. A 2-color FISH assay that employed probes at the 14q32 (immunoglobulin H) and 11q13 (dual-colored, directly labeled cyclin D1) loci was used. The number of single-fusion and double-fusion signals in 200 cells was counted. If ี 14% single-fusion signals or ี 1.5% double-fusion signals or both were present, then the sample was considered FISH positive. The findings were correlated with the cytologic, histologic, and immunophenotypic findings in each specimen. RESULTS. Of the 55 cytology specimens, 17 were mantle cell lymphomas, and 38 were nonmantle cell lymphomas, including 16 small lymphocytic lymphomas (9 of 16 in an accelerated phase), 5 large cell lymphomas, 5 follicular lymphomas, 7 transformed large cell lymphomas (Richter syndrome), 3 atypical lymphoid proliferations, and 2 low-grade B-cell lymphomas. All 17 mantle cell lymphomas were positive by FISH. In addition, there were six small lymphocytic lymphomas (two in accelerated phase), one transformed large cell lymphoma, and one large cell lymphoma of follicular origin positive by FISH. The mean number of single-fusion and double-fusion signals, respectively, was 36 and 33 in mantle cell lymphoma specimens and 19 and 3 in positive nonmantle cell lymphoma specimens. CONCLUSIONS. The detection of the t(11;14)(q13;q32) translocation by FISH analysis was helpful in diagnosing mantle cell lymphoma on FNA specimens. Doublefusion signals were more specific for mantle cell lymphoma than single-fusion signals. In rare instances, other non-Hodgkin lymphomas also showed increased numbers of single-fusion signals that were not necessarily indicative of the t(11; 14)(q13;q32) translocation. Therefore, in an initial diagnosis of mantle cell lymphoma, significant numbers of double-fusion FISH signals should be identified and interpreted in conjunction with the cytologic and immunologic studies.