Indolent Mantle Cell Lymphoma (MCL): A Retrospective Detailed Clinical and Morphological Analysis of 21 Patients, with Histological, Cytological, Cytogenetic, Interphase Genetic, Immunoglobulin Gene, and Gene Expression Profiling Analysis.
Authors: Thieblemont Catherine , Houlgatte Remi , Felman Pascale , Traverse-glehen Alexandra , Baseggio Lucile , Rolland Delphine , Callet-Bauchu Evelyne , Salles Gilles , Berger Francoise , Coiffier Bertrand 
Published: April 2020

Abstract
MCL is a well-defined lymphoid neoplasm characterized by a proliferation of mature B lymphocytes expressing CD5 and with a genetic hallmark, the t(11;14) (q13;q32) translocation leading to the overexpression of cyclin D1, considered as the initial oncogenic event. However this entity may show a spectrum of morphological features broader than initially described. Clinically most of the patients have a poor prognosis with a rapid acquisition of chemoresistance. It has been recently described that some patients may follow an indolent clinical evolution, with the possibility of confusion in diagnosis because of overlapping morphological features with other small B cell lymphomas such as marginal zone lymphoma (MZL) and small lymphocytic lymphoma (SLL). The aim of our study was to analyze patients treated for a B cell lymphoma bearing the t(11;14)(q13;q32) who had a good outcome with a long survival. We retrospectively selected 21 patients (pts) with a t(11;14) B cell lymphoma and who followed an indolent outcome defined by an overall survival of more than 5 years after no more than 1 therapeutic regimen. Feature review included morphologic aspect, immunophenotype, cytogenetics, immunoglobulin (Ig) variable heavy chain (VH) gene usage and mutation patterns. Expression of CD5, CD10, CD23, and CD43, were evaluated on CD19+ cells by FCM. Cytogenetic analysis consisted in conventional cytogenetics on fresh tissue samples completed by a FISH analysis against 11q, 12p, 17p, and 18p realized on fresh frozen material. We further analysed the gene expression profiling of available samples using quantitative real-time PCR using microfluidic cards designed with selected genes of 3 independent signatures (Rosenwald A, et al. Cancer Cell 2003 - Ruiz-Ballesteros E, et al. Blood 2005 - Thieblemont C, et al. Blood 2004). Clinical characteristics showed that median age was 61 (range 45–81). All pts had a good PS and presented with a disseminated disease: bone marrow and blood involvement in 19 (90%) and 11/17 (65%) pts, respectively; peripheral and profound nodes involvement in 15 (71%); and splenomegaly in 13 (62%). LDH and b2-microglobulin levels were elevated in 4 pts. None of the pts had a monoclonal component. IPI score was low in 18 (86%) pts. Splenectomy alone or with chemotherapy (chlorambucil or fludarabine in 4; CHOP in 1) was proposed in 7 pts; monochemotherapy (chlorambucil or fludarabine) in 4 pts, CHOP +/− rituximab (R) in 2 pts, CHOP +/− R followed by autotransplant in 8. One pt did not receive any treatment. With a median follow-up at 6.44 years, median overall survival was 9.18 years. Morphologic review distinguished 2 groups of cases: true MCL cases (MCL, n = 8) and BorderLine Cases (BLC, n=13). Among the 8 MCL and 13 BCL, 7 and 12 were CD5+, 1 and 4 CD5/CD23+, 4 and 5 CD43+, respectively. All cases exhibited a t(11;14), associated with a complex caryotype in 5/8 (62%) MCL and in 9/13 (69%) BLC. Chromosome 7q deletion (n=1) and trisomy chr3/3q (n=3) were present only in BLC cases. IgVH gene was unmutated in 10 cases (3 MCL, 7 BLC) and mutated in 4 (2 MCL, 2 BLC). The most common VH families were VH1 (n=4), VH 3 (n=8) and VH4 (n=3). From the gene expression profiling studies we selected 70 genes specific of the diagnosis of MCL, MZL and SLL. A set of 5 MCL, 5 SLL, and 5 MZL control samples allowed us to validate 25 out of these 70 genes. These 25 genes were further used to analyse MCL and BLC samples. All these samples exhibited a more heterogeneous profile than control samples. Three MCL were more similar to MCL samples, whereas two were closer to MZL samples. All the BLC exhibited a profile close to that of MZL. We further analysed these samples with the 18 gene-signature predicting MCL survival. This signature could not discriminate survival of these MCL and BCL pts. In conclusion, pts with B cell lymphoma bearing the translocation t(11;14)(q13;q32) and with an indolent outcome can be distinguished in at least 2 groups with different characteristics in terms of morphology, immunophenotype, caryotype, and molecular profiles. Using a 25 gene-signature, we found profiles similar to either MCL or MZL for MCL samples, and similar to MZL for BCL samples. The signature discriminating the survival of MCL could not discriminate these indolent MCL. These findings will be validated on a larger series.