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Lymphoplasmacytic lymphoma (LPL) is not a sharply delineated lymphoma entity, either morphologically, phenotypically, or clinically. The diagnosis is often made by excluding other small cell lymphomas with plasmacytic differentiation, thus a genetic diagnostic marker would be of great benefit. Conventional cytogenetic techniques have previously demonstrated a deletion of 6q in a proportion of cases, varying from 7 to 55%. In this report, we apply array-based comparative genomic hybridization on 11 LPL samples. Genomic aberrations were detected in 9 of 11 cases, and included gains and losses. In general, the number of genetic aberrations was relatively low (two to three abnormalities per case). Recurrent aberrations detected were deletion of 6q (two cases), deletion of chromosome 17 (two cases), gain of 3q (two cases), and gain of chromosome 7 (two cases). This report not only confirms the reported loss of 6q in a proportion of cases but also highlights the genetic heterogeneity of LPL, in accordance with the known immunophenotypical, morphological, and clinical diversity of the disease. [ABSTRACT FROM AUTHOR]

Telomere length was recently reported to correlate with cellular origin of B-cell malignancies in relation to the germinal center (GC). In this report, we measured telomere length by quantitative-PCR in 223 B-cell lymphomas/leukemias and correlated results with immunoglobulin (Ig) mutation status and immunostainings for GC/non-GC subtypes of diffuse large B-cell lymphoma (DLBCL). Shortest telomeres were found in Ig-unmutated chronic lymphocytic leukemia (CLL) [median telomere to single copy gene value (T/S) 0.33], differing significantly to Ig-mutated CLL (0.63). Contrary to this, mantle cell lymphomas (MCLs) exhibited similar telomere lengths regardless of Ig mutation status (0.47). Telomere length differed significantly between GC-like (0.73) and non-GC-like DLBCLs (0.43), and follicular lymphomas (FLs) had shorter telomeres (0.53) than GC-DLBCL. Hairy cell leukemias, which display Ig gene intraclonal heterogeneity, had longer telomeres (0.62) than FLs and non-GC-DLBCL, but shorter than GC-DLBCL. We conclude that although DLBCL and CLL subsets can be clearly distinguished, telomere length reflects many parameters and may not simply correlate with GC-related origin. [ABSTRACT FROM AUTHOR]

Abstract: Lymphoplasmacytic lymphoma (LPL) is a rare lymphoma thought to originate from a B cell stimulated to differentiate to a plasma cell, and which is usually accompanied by clonal IgM secretion, defining the diagnosis of Waldenström''s macroglobulinemia (WM). However, the immunoglobulin variable heavy chain (VH) gene usage and the somatic hypermutation status have not been widely investigated in LPL. LPL biopsies (CD19+/CD20+/CD22+/CD5−/CD10−/CD23−/κ +) from 14 patients were included most of whom had a serum IgM component of variable magnitude (two cases with IgG). Highly mutated VH genes (mean mutation rate 8%) were revealed in 13 of 14 LPLs, whereas one case displayed a germline VH gene configuration. Cloning of the VH gene rearrangements in nine cases showed homogeneous sequences without intraclonal heterogeneity. Furthermore, no bias in the VH gene usage was shown, with VH3, VH4, and VH1 gene family members represented. These data confirm that the LPL precursor cell has been exposed to the germinal centre environment, as indicated by extensive hypermutation, but also that the transformation event occurred after affinity maturation, since there was a lack of intraclonal variation. Additionally, the VH gene repertoire was not skewed in LPL/WM as has been demonstrated in other B cell malignancies. [Copyright &y& Elsevier]

Abstract: Hairy cell leukemia (HCL) is thought to arise from a post-germinal center (GC) B-cell, however the exact normal counterpart remains unclear. We performed VH gene analysis of 32 HCL cases, revealing somatically mutated VH genes (<98% homology) in 27 cases and unmutated VH genes in five cases, four of which displayed germline VH genes. Intraclonal heterogeneity was evident in the majority of eight mutated HCLs investigated, although at a lower level compared to GC-derived lymphomas. A novel finding of preferential VH3-30 gene usage was detected (19% of HCLs). Our data confounds the postulated post-GC origin in HCL considering (1) the finding of unmutated HCLs, generally correlating with a pre-GC origin, and (2) the presence of intraclonal variation in mutated HCLs. The latter suggests that the transformed B-cell was frozen when it still had an active mutation process, implying a closer relation to the GC than previously assumed. Furthermore, restricted VH3-30 usage indicates that antigen selection could be a promoting factor in HCL development. [Copyright &y& Elsevier]

Abstract: Mantle cell lymphoma (MCL) is considered to derive from naïve, pregerminal center (GC) CD5+ B-cells. However, the cell of origin has been questioned in recent studies that showed somatic hypermutations in the immunoglobulin (Ig) variable heavy chain (V H ) genes in subsets of MCL. To clarify this issue, we analyzed the IgV H genes for the presence of somatic hypermutations in 51 MCL cases. Twenty percent of the MCL cases displayed somatically mutated V H genes (defined as >2% mutated), whereas 80% showed unmutated V H genes. This finding suggests that MCL is a genetically heterogeneous disease, with the majority of cases originating from unmutated pre-GC B-cells and a subset deriving from more mature B-cells which have been exposed to the GC environment and have undergone somatic hypermutation. A biased V H gene usage has been demonstrated in several B-cell malignancies; however, this has not yet been investigated in MCL, although V H 4-34 overusage has been indicated by small studies. Interestingly, we found a restricted usage of three individual V H genes in our MCL material; V H 4-34 (22%), V H 3-21 (16%) and V H 5-51 (12%). This novel finding of preferential V H gene usage in half of the MCL cases may suggest an antigen driven process occurring in B-cells expressing specific V H genes, thus implicating that Ig specificity could be involved in mantle cell lymphoma development. [ABSTRACT FROM AUTHOR]

Abstract: Mantle cell lymphoma (MCL) is characterized by over-expression of cyclin Dl as a result of the characteristic t(11;14)(q13;q32). However, this translocation alone has proven not to be sufficient for lymphomagenesis, suggesting the involvement of additional alterations. We have characterized 35 cases of MCL by array comparative genomic hybridization with an average resolution of 0.97Mb distributed over the complete human genome. The most common alterations were losses in 1p13.2–p31.1, 6q16.2–q27, 8p21.3, 9p13.2–p24.3, 9q13–q31.3, 11q14.3–q23.3, 13q14.13–q21.31, 13q33.1–q34, and 22q11.23–q13.33 and gains involving 3q21.2–q29, 7p12.1–p22.3, 8q24.13–q24.23, and 18q21.33–q22.3. Four homozygous deletions were identified in totally three patients; two overlapping at 1p32.3, and two adjacent at 13q32.3. The homozygous deletions at 1p32.3 cover the CDKN2C locus (coding for p18), while the region at 13q32.3 does not encompass any known tumor suppressor genes. A gain in 3q was significantly associated with shorter survival (P =0.047). [Copyright &y& Elsevier]