Flow Cytometry and Fluorescence In Situ Hybridization Are Methods of Choice for Routine Diagnosis of Mantle Cell Lymphoma.

Mantle cell lymphoma (MCL) is a distinct clinicopathologic entity, characterized by expansion of lymphocytes with co-expression of CD5 and CD20 and frequent t(11;14) translocation. MCL and its morphological variants are frequently confused with other lymphoma subtypes. The aim of this study was to analyze a contribution of histopathology (HP), immunohistochemistry (IHC), flow cytometry (FCM) and cytogenetic analysis with fluorescence in situ hybridization (FISH) to ultimate diagnosis of MCL. We identified 66 pts diagnosed with MCL either by use of HP/IHC or/and FCM. Initial diagnosis was based on HP/IHC only, and was validated in 55 of 66 patients by combined use of HP/IH, FCM, and FISH. We examined paraffin sections IHC panel consisting of antibodies to CD3, CD5, CD20, CD23, CD43, and cyclin D1. FCM analysis was done by 3-colour direct immunofluorescence with extended panel of antibodies to CD5, CD10, CD11c, CD19, CD20, CD22, CD23, CD25, CD38, CD45, HLADR, FMC7, light and heavy chains. We used FISH to detect the t(11;14) in interphase cells of 24 cases of MCL. All 55 cases of MCL were CD20 positive and CD23 negative on IHC, 32 of 51 (63%) and 46 of 52 (88%) cases coexpressed the CD5 and CD43 antigens, respectively. Cyclin-D1 staining revealed nuclear positivity in 38 of 52 (73%) pts. Dual expression of CD5 and cyclin D1 - a finding highly reliable for MCL diagnosis on IHC, was seen in 49% (27/55) of pts. All MCL cases were CD20 (51/51) and CD19 (55/55) positive by FCM with higher intensity of CD20 expression compared to CD19 in 100% (51/51) of cases. CD5 and CD25 were coexpressed in 54 of 55 (98%) and in 43 of 49 (88%) pts respectively. CD22 (45/45) and HLADR (55/55) were positive in all cases. FMC7 and CD38 were found in 22 of 23 (96%) and in 19 of 23 (83%) patients, respectively. CD10, CD11c, CD23 were only seen on a subpopulation of cells with weak intensity in 15%(7/48), 13% (6/45), and 11% (5/46) pts., respectively. MCL cells expressed moderate intensity monoclonal surface light chains in 47 of 52 (90%) pts with L light chain predominance and IgM+/IgD+ in 16 of 17 (94%) pts. False or incomplete initial diagnosis based mainly on lymph node HP/IHC was found in 35 of 66 (53%) cases. False FCM diagnosis of MCL was found in 2 of 66 (3%) cases. Results of FCM and FISH were consistent with the MCL diagnosis in 92% (22/24) of patients, in our hands. Our data indicate that the phenotypic pattern of MCL by FCM is remarkably constant among patients. As MCL represents a frequent diagnostic challenge, a combined use of FCM and FISH may provide an optimum solution.