Alexandra Valera

SOX11 expression is highly specific for mantle cell lymphoma and identifies the cyclin D1-negative subtype

Cyclin D1-negative mantle cell lymphoma is difficult to distinguish from other small B-cell lymphomas. This study shows that SOX11 mRNA and nuclear protein expression is a highly specific marker for both cyclin D1-positive and negative mantle cell lymphoma. See related perspective article on page 1488. Background Cyclin D1-negative mantle cell lymphoma is difficult to distinguish from other small B-cell lymphomas. The clinical and pathological characteristics of patients with this form of lymphoma have not been well defined. Overexpression of the transcription factor SOX11 has been observed in conventional mantle cell lymphoma. The aim of this study was to determine whether this gene is expressed in cyclin D1-negative mantle cell lymphoma and whether its detection may be useful to identify these tumors. Design and Methods The microarray database of 238 mature B-cell neoplasms was re-examined. SOX11 protein expression was investigated immunohistochemically in 12 cases of cyclin D1-negative mantle cell lymphoma, 54 cases of conventional mantle cell lymphoma, and 209 additional lymphoid neoplasms. Results SOX11 mRNA was highly expressed in conventional and cyclin D1-negative mantle cell lymphoma and in 33% of the cases of Burkitt’s lymphoma but not in any other mature lymphoid neoplasm. SOX11 nuclear protein was detected in 50 cases (93%) of conventional mantle cell lymphoma and also in the 12 cyclin D1-negative cases of mantle cell lymphoma, the six cases of lymphoblastic lymphomas, in two of eight cases of Burkitt’s lymphoma, and in two of three T-prolymphocytic leukemias but was negative in the remaining lymphoid neoplasms. Cyclin D2 and D3 mRNA levels were significantly higher in cyclin D1-negative mantle cell lymphoma than in conventional mantle cell lymphoma but the protein expression was not discriminative. The clinico-pathological features and outcomes of the patients with cyclin D1-negative mantle cell lymphoma identified by SOX11 expression were similar to those of patients with conventional mantle cell lymphoma. Conclusions SOX11 mRNA and nuclear protein expression is a highly specific marker for both cyclin D1-positive and negative mantle cell lymphoma.

Landscape of somatic mutations and clonal evolution in mantle cell lymphoma

Significance This is a comprehensive whole-genome/whole-exome analysis of mantle cell lymphoma (MCL). We sequenced 29 MCL cases and validated the findings by target sequencing of 172 additional tumors. We identified recurrent mutations in genes regulating chromatin modification and genes such as NOTCH2 that have a major impact on clinical outcome. Additionally, we demonstrated the subclonal heterogeneity of the tumors already at diagnosis and the modulation of the mutational architecture in the progression of the disease. The identification of new molecular mechanisms may open perspectives for the management of MCL patients. Mantle cell lymphoma (MCL) is an aggressive tumor, but a subset of patients may follow an indolent clinical course. To understand the mechanisms underlying this biological heterogeneity, we performed whole-genome and/or whole-exome sequencing on 29 MCL cases and their respective matched normal DNA, as well as 6 MCL cell lines. Recurrently mutated genes were investigated by targeted sequencing in an independent cohort of 172 MCL patients. We identified 25 significantly mutated genes, including known drivers such as ataxia-telangectasia mutated (ATM), cyclin D1 (CCND1), and the tumor suppressor TP53; mutated genes encoding the anti-apoptotic protein BIRC3 and Toll-like receptor 2 (TLR2); and the chromatin modifiers WHSC1, MLL2, and MEF2B. We also found NOTCH2 mutations as an alternative phenomenon to NOTCH1 mutations in aggressive tumors with a dismal prognosis. Analysis of two simultaneous or subsequent MCL samples by whole-genome/whole-exome (n = 8) or targeted (n = 19) sequencing revealed subclonal heterogeneity at diagnosis in samples from different topographic sites and modulation of the initial mutational profile at the progression of the disease. Some mutations were predominantly clonal or subclonal, indicating an early or late event in tumor evolution, respectively. Our study identifies molecular mechanisms contributing to MCL pathogenesis and offers potential targets for therapeutic intervention.

Gene expression profiling and not immunophenotypic algorithms predicts prognosis in patients with diffuse large B-cell lymphoma treated with immunochemotherapy

Diffuse large B-cell lymphomas (DLBCLs) can be divided into germinal-center B cell-like (GCB) and activated-B cell-like (ABC) subtypes by gene-expression profiling (GEP), with the latter showing a poorer outcome. Although this classification can be mimicked by different immunostaining algorithms, their reliability is the object of controversy. We constructed tissue microarrays with samples of 157 DLBCL patients homogeneously treated with immunochemotherapy to apply the following algorithms: Colomo (MUM1/IRF4, CD10, and BCL6 antigens), Hans (CD10, BCL6, and MUM1/IRF4), Muris (CD10 and MUM1/IRF4 plus BCL2), Choi (GCET1, MUM1/IRF4, CD10, FOXP1, and BCL6), and Tally (CD10, GCET1, MUM1/IRF4, FOXP1, and LMO2). GEP information was available in 62 cases. The proportion of misclassified cases by immunohistochemistry compared with GEP was higher when defining the GCB subset: 41%, 48%, 30%, 60%, and 40% for Colomo, Hans, Muris, Choi, and Tally, respectively. Whereas the GEP groups showed significantly different 5-year progression-free survival (76% vs 31% for GCB and activated DLBCL) and overall survival (80% vs 45%), none of the immunostaining algorithms was able to retain the prognostic impact of the groups (GCB vs non-GCB). In conclusion, stratification based on immunostaining algorithms should be used with caution in guiding therapy, even in clinical trials.

IG/MYC rearrangements are the main cytogenetic alteration in plasmablastic lymphomas.

Plasmablastic lymphoma (PBL) is an aggressive lymphoma characterized by a terminally differentiated B-cell phenotype that usually occurs in the immunocompromised or elderly patients. Although the clinical and pathologic characteristics of these tumors have been defined, the genetic alterations involved in their pathogenesis are not well known. In this study, we have investigated the chromosomal alterations of MYC, BCL2, BCL6, MALT1, PAX5, and IGH loci using fluorescence in situ hybridization in 42 PBL and 3 extracavitary primary effusion lymphomas. MYC rearrangements were identified in 20 of 41 (49%) PBL and the immunoglobulin (IG) genes were the partners in most tumors. MYC rearrangements were more common in Epstein-Barr virus (EBV)-positive (14 of 19, 74%) than EBV-negative (9 of 21, 43%) tumors (P<0.05). No rearrangements of BCL2, BCL6, MALT1, or PAX5 were detected in any PBL but gains of these loci were observed in 31% to 41% of the cases examined. Twelve of the 40 PBL in which 3 or more loci could be investigated had multiple simultaneous gains in 3 or more loci. No differences in the survival of the patients according to MYC were observed but the 4 patients with the longest survival (>50 mo) had no or low number of gains (<3). No rearrangements of any of these loci were seen in the primary effusion lymphomas. In conclusion, PBL are genetically characterized by frequent IG/MYC translocations and gains in multiple chromosomal loci. The oncogenic activation of MYC in these lymphomas may be an important pathogenetic element associated with EBV infection.

MYC protein expression and genetic alterations have prognostic impact in patients with diffuse large B-cell lymphoma treated with immunochemotherapy.

MYC alterations influence the survival of patients with diffuse large B-cell lymphoma. Most studies have focused on MYC translocations but there is little information regarding the impact of numerical alterations and protein expression. We analyzed the genetic alterations and protein expression of MYC, BCL2, BCL6, and MALT1 in 219 cases of diffuse large B-cell lymphoma. MYC rearrangement occurred as the sole abnormality (MYC single-hit) in 3% of cases, MYC and concurrent BCL2 and/or BCL6 rearrangements (MYC double/triple-hit) in 4%, MYC amplifications in 2% and MYC gains in 19%. MYC single-hit, MYC double/triple-hit and MYC amplifications, but not MYC gains or other gene rearrangements, were associated with unfavorable progression-free survival and overall survival. MYC protein expression, evaluated using computerized image analysis, captured the unfavorable prognosis of MYC translocations/amplifications and identified an additional subset of patients without gene alterations but with similar poor prognosis. Patients with tumors expressing both MYC/BCL2 had the worst prognosis, whereas those with double-negative tumors had the best outcome. High MYC expression was associated with shorter overall survival irrespectively of the International Prognostic Index and BCL2 expression. In conclusion, MYC protein expression identifies a subset of diffuse large B-cell lymphoma with very poor prognosis independently of gene alterations and other prognostic parameters.

Assessment of SOX11 expression in routine lymphoma tissue sections: characterization of new monoclonal antibodies for diagnosis of mantle cell lymphoma.

The diagnosis of mantle cell lymphoma (MCL) can be difficult, especially when no t(11;14) translocation and cyclin D1 overexpression can be detected. In such cases, the transcription factor SOX11 represents an important diagnostic marker, as it is expressed in most MCLs and, in particular, in all cyclin D1-negative MCLs reported so far. A reliable anti-SOX11 antibody is therefore a very useful tool for routine diagnosis. Here, we characterize the new monoclonal anti-SOX11 antibodies, suitable for Western blot assay and immunohistochemistry (IHC) on formalin-fixed paraffin-embedded tissue; we tested them on a large series of primary lymphoid tumors and compared these results with those of other routinely used antibodies. Moreover, we show that IHC results depend on transcription levels of SOX11, which suggests that posttranscriptional and posttranslational modifications do not significantly affect cutoff levels for IHC detection of SOX11.

Recurrent mutations of NOTCH genes in follicular lymphoma identify a distinctive subset of tumours

Follicular lymphoma (FL) is one of the most common malignant lymphomas. The t(14;18)(q32;q21) translocation is found in about 80% of cases and plays an important role in lymphomagenesis. However, the molecular mechanisms involved in the development and transformation of this lymphoma are not fully understood. Gain‐of‐function mutations of NOTCH1 or NOTCH2 have recently been reported in several B cell lymphoid neoplasms but the role of these mutations in FL is not known. In this study we investigated the mutational status of these genes in 112 FLs. NOTCH1 and NOTCH2 mutations were identified in five and two cases, respectively (total 7/112, 6.3%). All mutations predicted for truncated protein in the PEST domain and were identical to those identified in other B cell lymphoid neoplasms. NOTCH‐mutated FL cases were characterized by lower frequency of t(14;18) (14% versus 69%, p = 0.01), higher incidence of splenic involvement (71% versus 25%, p = 0.02) and female predominance (100% versus 55%, p = 0.04). A diffuse large B cell lymphoma (DLBCL) component was more frequently identified in NOTCH‐mutated FL than in wild‐type cases (57% versus 18%, p = 0.03). These results indicate that NOTCH mutations are uncommon in FL but may occur in a subset of cases with distinctive, characteristic, clinicopathological features. Copyright

Plasmablastic transformation of low-grade B-cell lymphomas: report on 6 cases.

Histologic transformation of low-grade B-cell lymphoma to diffuse large B-cell lymphoma is associated with poor prognosis. Although plasma cell differentiation is common in these lymphomas, an overt plasmablastic transformation (PBL-T) has been only rarely reported. We report 6 cases of PBL-T occurring in 3 chronic lymphocytic leukemias (CLL) and 3 follicular lymphomas. Five patients were men, and the mean age was 65 years (range, 52 to 72 y). None of them had history of immunodeficiency. In 3 cases the PBL-T occurred 34 to 85 months after the initial diagnosis, and in 3 it was detected simultaneously with the small cell component at diagnosis. All patients received chemotherapy after transformation, and 4 died 4 to 24 months after this diagnosis. In 3 cases, PBL-T occurred in an extranodal site. All PBL-Ts had immunoblastic morphology with admixed plasma cells, were CD20 and PAX5 negative, expressed &lgr; light chain, and 5 were CD138 positive. All cases were negative for HHV8, and only 1 PBL-T was Epstein-Barr virus positive. Evidence of a clonal relationship between the small cell and PBL-T components was found in 5 cases. In 2 CLL cases, both components had 13q deletions, and in all follicular lymphoma cases both components harbored the t(14;18) translocation. MYC translocations were observed in 2 cases transformed from a CLL. In conclusion, PBL-T expands the clinicopathologic spectrum of the transformation of low-grade B-cell lymphomas. These transformed tumors are clinically, histologically, and phenotypically similar to primary plasmablastic lymphomas, but they are not associated with immunodeficiency and rarely have Epstein-Barr virus infection or MYC alterations.

ALK-positive large B-cell lymphomas express a terminal B-cell differentiation program and activated STAT3 but lack MYC rearrangements

ALK-positive large B-cell lymphoma is an aggressive lymphoid neoplasm characterized by a monomorphic proliferation of immunoblast-like cells expressing a plasmablastic phenotype and carrying ALK rearrangements. MYC rearrangements are frequent in plasmablastic lymphomas, advanced plasma cell myelomas and a subgroup of diffuse large B-cell lymphomas, but their presence in ALK-positive large B-cell lymphomas is unknown. MYC expression is downregulated by BLIMP1, a master modulator of plasma cell differentiation. BLIMP1 and MYC are upregulated by STAT3, a signal transducer activated by ALK. To determine the role of BLIMP1, MYC and STAT3 in the pathogenesis of ALK-positive large B-cell lymphomas, we investigated MYC rearrangement and the expression of MYC, phosphorylated STAT3, BLIMP1, PAX5 and XBP1 in 12 ALK-positive large B-cell lymphomas. All cases expressed ALK with a granular cytoplasmic pattern. Nine cases had a split signal consistent with an ALK rearrangement. Three additional cases showed a deletion of the 5′ or 3′ end of the ALK probe consistent with cryptic translocation. PAX5 was virtually negative in all cases tested, whereas BLIMP1 was expressed in all tumors and XBP1 in 11 of 12. Phosphorylated STAT3 was observed in all cases with a strong and diffuse nuclear pattern. MYC rearrangements were not identified in any tumor, but MYC gains and amplification were detected in six cases and one case, respectively. MYC protein was expressed in all tumors independently of MYC gene alterations. These results indicate that ALK-positive large B-cell lymphomas express a complete plasmablastic differentiation program but, contrary to plasmablastic lymphomas, do not have MYC rearrangements. STAT3 is constantly activated and may be an alternative mechanism to promote MYC expression in these tumors. The relevance of the ALK/STAT3 pathway in the pathogenesis of ALK-positive large B-cell lymphomas may offer an attractive target for new therapies.

Pigmented spindle cell nevus: clues for differentiating it from spindle cell malignant melanoma. A comprehensive survey including clinicopathologic, immunohistochemical, and FISH studies.

Pigmented spindle cell nevus (PSCN), also known as Reed nevus, is a distinctive melanocytic tumor that can show worrisome clinical and histologic features mimicking a malignant melanoma. From a series of 46 pigmented spindle cell melanocytic lesions, including 22 PSCN and 24 spindle cell malignant melanomas (SCMMs), we collected clinical and histopathologic characteristics and evaluated cell cycle and apoptosis regulators by immunohistochemistry. Moreover, fluorescence in situ hybridization (FISH) using probes targeting 6p25 (RREB1), 11q13 (CCND1), 6q23 (MYB), and centromere 6 was performed. PSCN presented in younger people, frequently in women, and were small lesions under 7 mm in diameter affecting the lower limbs, whereas SCMMs arose more frequently in the trunk, upper limbs, and head and neck region. Histologically, symmetry, good lateral demarcation, and uniformity of cellular nests were significantly differential features of PSCN, whereas pagetoid and adnexal spread were frequently seen in both tumors. Immunohistochemical markers that significantly differed from melanomas were Ki-67, cyclin D1, and survivin. FISH was positive in 1 of 15 PSCN and was negative in 4 of 15 SCMMs. These results correlated to a sensitivity of 73% and a specificity of 93%. In conclusion, in the evaluation of pigmented spindle cell melanocytic tumors, the integration of clinical and histologic assessment is essential. However, ancillary techniques such as proliferation antigen Ki-67, cyclin D1, survivin, and FISH can be useful as adjunctive tools.