The Genetic Basis of Hepatosplenic T-cell Lymphoma

Hepatosplenic T cell lymphoma (HSTL) is a rare and lethal lymphoma; the genetic drivers of this disease are unknown. Through whole exome sequencing of 68 HSTLs, we define recurrently mutated driver genes and copy number alterations in the disease. Chromatin modifying genes including SETD2, INO80 and ARID1B were commonly mutated in HSTL, affecting 62% of cases. HSTLs manifest frequent mutations in STAT5B (31%), STAT3 (9%), and PIK3CD (9%) for which there currently exist potential targeted therapies. In addition, we noted less frequent events in EZH2, KRAS and TP53. SETD2 was the most frequently silenced gene in HSTL. We experimentally demonstrated that SETD2 acts as a tumor suppressor gene. In addition, we found that mutations in STAT5B and PIK3CD activate critical signaling pathways important to cell survival in HSTL. Our work thus defines the genetic landscape of HSTL and implicates novel gene mutations linked to HSTL pathogenesis and potential treatment targets

Immunoglobulin Light Chain Use and Characteristics in the Chlamydophila Psittaci negative MALT Lymphomas of the Ocular Adnexa

Abstract Abstract 1597 Ocular adnexal mucosa associated lymphoid tissue lymphomas (OAMALTL) are the most common lymphomas of the eye. The potential roles for specific antigens in these lymphomas are still controversial. Previously we examined the usage and mutations of the IGVH in Chlamydophila (C) psittaci-negative OAMALTL, demonstrating biased use of the IGHV4 family and IGHV4–34 gene and evidence for antigen selection (PLoS One. 2011;6(12):e29114). However, there have been no previous reports characterizing the Ig light chain (IGKV/IGLV) usage and properties in OAMALTL. Herein, we examined IGKV/IGLV gene usage and mutations in 34 C. psittaci-negative OAMALTL originating from the orbit (15), conjunctivae (14) and lacrimal gland (5). Clonal potentially functional IGKV/IGLV gene sequences were identified in 30 tumors (18 kappa and 12 lambda). Among the 7 kappa light chain families, IGKV1 (n=5, 28%), IGKV2 (n=1, 6%), IGKV3 (n=8, 44%) and IGKV4 (n=4, 22%) were observed. Among the 8 lambda chain families, IGLV2 (n=5, 42%), IGLV3 (n=1, 8%), IGLV6 (n=1, 8%), IGLV7 (n=3, 25%) and IGLV8 (n=2, 17%) were detected. In comparison with the IGKV and IGLV repertoire employed in normal peripheral blood B-lymphocytes, an overrepresentation of the IGKV4 family (P<0.01) was observed in the analyzed cohort of tumors. No statistically significant difference in the use of other kappa and lambda light chain families was observed. In the most commonly used IGKV3 family, only 2 (IGKV3–20*01 (n=6) and IGKV3–15*01 (n=2)) of the 7 family members were used by the OAMALTL. The IGKV3–20*01 allele was used at a greater frequency than in normal peripheral blood B-lymphocytes (p=0.02). The observed frequency of the allele in OAMALTL (20%) is higher than the previously reported frequency in other non-MALT lymphoma types. Of the six cases which utilized the IGKV3–20*01 allele, corresponding heavy chains were available for five cases. Three of the IGKV3–20*01 alleles paired with the IGHV4–34 allele, one paired with the IGHV3–23 allele and one paired with the IGHV1–69 allele. Interestingly, each of these three alleles has been previously implicated in autoreactivity. The IGKV4-1*01 allele was observed to pair with IGHV3–74 (n=2), IGHV1–24 (n=1) and IGHV2–5 (n=1), respectively. Of the 30 clonal tumor sequences, 27 displayed mutations from germline. The average percent homology to germline was 96.35%. Most mutated cases (14 out of 27, 52%) exhibited less than a 2% difference from their original germline sequence. Four of the six tumors utilizing the IGKV3–20*01 allele exhibited more than 2% mutation away from germline, with the remaining two sequences unmutated. Three of the four tumors employing IGKV4-1*01 exhibited greater than 2% mutation away from germline. No acquired N-glycosylation sites were observed in the OAMALTL. To analyze for potential selective pressure exerted by antigens, we utilized the BASELINe algorithm, which assesses for both presence and strength of antigen selection. 23 sequences exhibited evidence of selection in the CDR regions, while 26 sequences exhibited evidence of selection in the FR regions. Of the 26 sequences for which paired light and heavy chains were available, 9 heavy chains exhibited strong evidence of selection (8 in FR, 1 in CDR) and 5 light chain exhibited strong evidence of selection (all in FR). Two patients' tumors exhibited strong evidence of selection in both heavy and light chains. A recurrent mutation was observed in the FR2 region of sequences derived from the IGKV3–20*01, with three of six cases showing an acquisition of histidine in place of glutamine at position 39. An analysis of the tumor derived CDR3 regions did not reveal stereotyped sequence determinants and showed no homology to other known bacterial binding antibodies. Our findings demonstrate that C. psittaci negative OAMALTL exhibit biased usage of IGKV families and genes with evidence of antigen selection. Combined with our previous findings, we demonstrate the frequent use and common pairing of IGVH and IGKV genes, which are usually used by autoantibodies, suggesting that the C. psittaci negative OAMALTL encoded immunoglobulins may be directed to autoantigens. Indeed, generated recombinant immunoglobulins derived from multiple OAMALTLs react to self and not to bacterial antigens. These findings and the identity of the autoantigens will be presented at the meeting. Disclosures: No relevant conflicts of interest to declare

CD30 Expression in Diffuse Large B-Cell Lymphoma and Its Relation to Important Clinical and Biological Disease Features

Abstract Abstract 1592 Background: CD30 is a well-known diagnostic marker in both anaplastic large cell lymphoma (ALCL) and classical Hodgkin's lymphoma (CHL). Recently the chimeric drug brentuximab vedotin that combines an anti-CD30 monoclonal antibody with the anti-tubulin agent monomethyl auristatin E demonstrated activity in patients with relapsed ALCL and CHL. Previous observational studies have suggested that CD30 may be expressed in 10 to 20% of DLBCLs. It is possible that CD30+ DLBCLs may show different biologic behavior and be amenable to anti-CD30 therapy. The aim of this study was to determine the prevalence of CD30 expression in DLBCL by immunohistochemistry and explore possible relationships with important clinical and biologic variables of DLBCL. Methods: We retrospectively identified cases of DLBCL diagnosed between July 2003 and July 2012 at our institution. Eligible cases included patients with diagnosis of DLBCL irrespective of anatomic site or tumor stage. The diagnosis of DLBCL was based on the current WHO 2008 criteria. The following large B cell lymphoma subtypes were excluded from this analysis: post-transplant lymphoproliferative disorders with DLBCL morphology, Primary Mediastinal large cell lymphoma and the unclassifiable lymphomas with features intermediate between either DLBCL and Burkitt's lymphoma or between DLBCL and Hodgkin's lymphoma. Immunohistochemistry was performed as part of the routine workup of the cases (Monoclonal Mouse Anti-Human CD30, Dako) and CD30 was considered positive when ≥30% of neoplastic cells stained positive. DLBCLs were classified into germinal center (GC) or non-GC subtypes applying the Hans algorithm. Logistic regression analysis was performed to assess association between selected variables and CD30 expression. Results: A total of 333 cases of DLBCL were eligible for this study and of these 148 cases (44.4%) had CD30 results available. Selected demographic, clinical and histological characteristics were similar between cases on which CD30 IHC was performed compared to those in which CD30 IHC was not performed (data not shown), arguing against a selection bias in the performance of CD30 immunohistochemistry in these cases. Twenty-three percent (95% CI: 16.2% – 29.8%) of DLBCL tumors expressed CD30. CD30 expression was not significantly different between females and males (27.6% and 20.0% respectively, p = 0.28). The patients with CD30+ DLBCLs were 11.6 years younger than those with CD30- DLBCLs (95% CI: 5.3 – 17.9 years). The optimal cutoff age for CD30 expression was 47 years (ROC area under the curve: 0.70, p < 0.001). CD30 expression was more frequent in nodal and BCL2+ DLBCLs (Table 1). There was a non-significant difference between the expression of CD30 in non-GC type compared to GC type DLBCL with a pronounced trend for higher proportion of CD30 positivity in non-GC DLBCL (Table 1). CD30 expression was not significantly different in Epstein-Barr virus positive (EBV) compared to EBV negative DLBCLs (Table 1). Conclusions: CD30 is expressed in approximately 20% of all DLBCL and is more frequently expressed in younger patients and in BCL2+ DLBCLs. Although statistical significance was not reached, a trend towards more frequent CD30 expression in non-GC DLBCLs was observed. The increased expression of CD30 in the younger age group is intriguing, as other CD30+ neoplasms (CD30+ ALCL, CHL, and embryonal carcinoma) are also commonly observed in younger patients. The development of brentuximab vedotin and its well established effectiveness in other types of relapsed lymphomas opens the possibility of its applicability in CD30+ DLBCLs. Disclosures: No relevant conflicts of interest to declare

Frequency and extent of CD30 expression in diffuse large B-cell lymphoma and its relation to clinical and biologic factors: a retrospective study of 167 cases

Previous studies have suggested that CD30 may be expressed in diffuse large B-cell lymphomas (DLBCLs). However, the prevalence of CD30 + DLBCLs and extent of CD30 expression within an individual tumor have not been fully evaluated. The aim of this study was to determine the frequency and extent of CD30 expression in DLBCLs, and explore possible relationships between CD30 expression and clinical and biologic variables. We retrospectively identified and analyzed 167 cases of CD30 + DLBCLs from our pathology archive. Twenty-one percent (95% confidence interval [CI]: 14.8-27.1%) of these cases expressed CD30, and in 52% of them CD30 was positive in > 80% of tumor cells. CD30 expression was more frequent in DLBCLs with non-germinal center origin phenotype, BCL2 + DLBCLs and in patients ≤ 47 years old. There was significant interaction of BCL2 expression with age and subtype of DLBCL. A multivariate analysis performed in BCL2 + DLBCLs showed a higher frequency of CD30 + cases in non-germinal center DLBCLs (odds ratio [OR]: 6.5, 95% CI: 1.1-36.5) and in patients ≤ 47 years old (OR: 6.9, 95% CI: 1.5-29.5). These associations could suggest a common biologic pathogenesis. The effectiveness of anti-CD30 drugs in other lymphomas opens the possibility for their use in patients with CD30 + DLBCLs

Clinical Features, Treatment Outcome, and Predictive Biomarkers In Adult T-Cell Leukemia/Lymphoma: University Of Miami Experience

Abstract Introduction Adult T-cell leukemia/lymphoma (ATLL) is a rare aggressive malignancy with a poor prognosis caused by HTLV-1. Miami is proximal to the Caribbean where HTLV-I is endemic, and we encounter a relatively high number of ATLL cases. Herein, we have performed the largest single institution retrospective analysis of ATLL patients (pts) to date in the U.S. We studied ATLL patient characteristics, treatment patterns, and disease outcome. In addition, we investigated the expression of IRF-4/MUM-1 in available specimens. Previously, our group demonstrated an association between lack of IRF-4/MUM-1 and response to AZT-interferon-alpha (AZT/IFNa) therapy in a small ATLL cohort. IRF-4/MUM-1 is a putative NF-kB target gene that encodes a transcription factor. IRF-4/MUM-1 expression has been associated with interferon resistance in preclinical studies, and is a poor prognostic marker in some lymphomas. One of our objectives is evaluate and validate IRF-4/MUM-1 as a potential biomarker for treatment selection and outcome in ATLL. Methods We analyzed 125 pts diagnosed with ATLL in UM/JMH between 1987 and 2013. We evaluated MUM-1 protein expression using immunohistochemistry (IHC) on either tissue sections, or cytospins prepared from CD4+-enriched peripheral blood leukemic specimens using 30% nuclear staining as a cut-off positive value, or by western blot (WB) analysis in some cases where fresh or DMSO preserved ATLL cells were not available. Kaplan-Meier survival curves, log-rank test where used for survival analysis. Mann-Whitney's U test was used to compare non-normally distributed continuous variables. Pearson's chi-squared or Fischer's exact tests were used to compare categorical variables. Results ATLL pts were 45% male and 55% female with a median age of 51 (17-91). The great majority of pts were Afro-Caribbean (82%), followed by U.S. African American (12%) and South American (6%). A total of 109 pts have been analyzed for treatment response so far, including 51 acute, 50 lymphomatous (L), 6 chronic (5 unfavorable), and 2 smoldering types. The median overall survival (OS) for acute and L was 6 and 10 months respectively, and not reached for chronic and smoldering types (figure 1). Fifty-six pts (34 acute, 14 L, 5 unfavorable chronic, 1 chronic, and 2 smoldering) were treated with high-dose AZT/IFNa as first line therapy. The complete and overall response rates (CR and ORR) after AZT/IFNa for acute/unfavorable chronic (A/UC) vs. L types were 25% vs. 0.7%, and 54% vs. 21% respectively. Seventy-seven pts received chemotherapy at some point during their treatment. The CR rate and ORR for A/UC vs. L-type pts treated with chemotherapy-based regimens were 40 % vs. 21%, and 70% vs. 77% respectively. However, we observed a significantly longer median progression-free survival (PFS) and sustained responses in pts with A/UC ATLL who achieved a CR with AZT/IFNa (168.1 wks), as compared to chemotherapy (61.1 wks), which translated into an overall survival benefit. Next, in order to determine whether IRF-4/MUM-1 predicted response to AZT/IFNa, 66 ATLL cases were analyzed by IHC and/or WB. The results showed that 38.5% of A/UC were IRF-4/MUM-1+ as compared to 82.1% in the L type (<P.0001). Evaluable pts for AZT/IFNa response demonstrated that 55% of A/UC MUM-1(-) cases had a CR as compared to 0% in MUM-1+ pts (P=.009). In the L group, AZT/IFNa responses were minimal and were mainly limited to stable disease. Subgroup analysis showed that median OS for MUM-1(-) vs. MUM-1+ in A/UC subtype was 38.4 wks vs. 27.6 wks (P=0.275) (figure 2), respectively. In the L subtype, median OS for MUM-1(-) vs. MUM-1+ was 25.7 wks vs. 60.3 wks (P=0.02) (figure 3), respectively. Finally, the median PFS in AZT/IFNa-treated A/UC pts favored the MUM-1(-) as compared to MUM-1+ cases. Conclusion Our data demonstrate that AZT/IFNa therapy is beneficial in leukemic type (A/UC) lacking IRF-4/MUM-1 expression, while L type is generally resistant to this treatment. On the other hand, IRF-4/MUM-1 expression is associated with a favorable outcome in L subtype. We have identified IRF-4/MUM-1 expression as a predictive marker that could be used in deciding upfront therapy (i.e. AZT/IFNa vs. standard chemotherapy) in leukemic ATLL subtypes. Our study findings must be confirmed and validated in a larger ATLL cohort. Disclosures: No relevant conflicts of interest to declare

Gene Expression Analysis Of Plasmablastic Lymphoma Identifies Down Regulation Of B Cell Receptor Signaling and Additional Unique Transcriptional Programs

Abstract Plasmablastic lymphoma (PBL) is currently recognized as a distinct sub-type of diffuse large B-cell lymphoma (DLBCL), but remains a poorly characterized B-cell malignancy. We conducted gene expression profiling of 15 PBL, 10 DLBCL, and 5 EOP (extraosseous isolated plasmacytoma). 864 genes were significantly over- or under-expressed (at<1% false discovery rate) uniquely in one of these diseases relative to the other two. Of these, 102 were highly expressed in PBL relative to DLBCL and EOP, while 166 showed low expression in PBL. This set of 268 genes defined a distinct transcriptional program operating in PBL. Among these were surface markers such as CD320, CD300A, and IL6 receptor, as well as the cytokine Oncostatin M, which was highly expressed in PBL but almost never expressed in DLBCL or EOP. CD320 plays a role in generation and proliferation of plasma cells in the germinal center in response to IL-10 stimulation, while the immunoglobulin superfamily member CD300 is variably expressed across the hematopoietic hierarchy. The apoptosis-inducer BAX (Bcl-2 associated X protein) was highly expressed in PBL, similar to reports in plasma cell neoplasms. In addition the CpG methyltransferase gene Dnmt3b showed high expression levels in PBL. By comparing malignancy-specific gene expression patterns to known biological pathways, we found that expression of components of the B-cell receptor signaling pathway (Cd79a, Cd79b, Blk, Lyn, Syk, Ptprc, Csk, Pik3cd, Swap70, and Rel) were repressed by 2-fold or more on average in PBL relative to DLBCL. We observed a similar pattern in EOP relative to DLBCL. In contrast, mitochondrial genes were more highly expressed in PBL than in DLBCL. Analysis against a large compendium of sets of transcription factor targets from motif and ChIP analyses identified that targets of MYB, a major transcriptional regulator of hematopoietic differentiation, were up-regulated in PBL; whereas targets of NFKB1 were repressed relative to DLBCL. Both PBL and EOP highly expressed genes that have previously been described as up-regulated in plasmacytomas. To further investigate the potential cell of origin of these malignancies, we compared genes expressed in PBL, DLBCL, and EOP to genes that are highly expressed in specific sub-types of B-cells. Genes highly expressed in plasma cells relative to other types of B-cells were highly expressed in PBL and EOP compared to DLBCL. Notably, this included the transcription factor XBP1 (X-box binding protein 1), which is a critical regulator of plasma cell differentiation. The plasma cell marker CD138 (syndecan-1, encoded by the Sdc1 gene) was also over-expressed in the PBL and EOP samples. We have validated the array data by reanalyzing expression of four candidate genes (Lyn, Syk, SPIB, and Swap70) by real time PCR. These four genes were highly expressed in DLBCL, but their expression was low in both in PBL and EOP. The observed overexpression of Swap70 in DLBCL as compared to PBL and EOP was subsequently validated by immunohistochemistry (IHC). Immunostaining for Swap70 was performed in all 30 cases used for array analysis and was negative in all cases of PBL (0/15 positive) and EOP (0/5 positive) but was diffusely positive in all but one of the DLBCLs (9/10 positive). Swap70 analysis by IHC was subsequently performed in 7 additional cases of DLBCL and was diffusely positive in all of these cases (7/7), thus suggesting that immunohistochemical analysis for Swap70 may be useful in differentiating PBL and EOP from DLBCL. Overall our results provide insight into the unique transcriptional programs distinguishing PBL from morphologic and clinical mimics DLBCL and EOP, as well as identify similarities between them. Most notably, we observed that B-cell receptor signaling pathway genes are significantly down-regulated in PBL and EOP compared to DLBCL. These findings corroborate the downregulation of surface immunoglobulin expression as seen in PBL and EOP and suggest a biologic similarity between these two neoplasms. Among normal B-cell sub-populations, PBL and EOP were most similar in their expression patterns to plasma cells and plasmablasts in that they expressed several well-known plasma cell markers. These findings additionally identify novel candidate genes that provide opportunities for further phenotypic and functional characterization of these neoplasms. Disclosures: No relevant conflicts of interest to declare

Adult renal cell carcinoma with rhabdoid morphology represents a neoplastic dedifferentiation analogous to sarcomatoid carcinoma

Renal cell carcinoma (RCC) with rhabdoid morphology (RCC-RM) is a recently described variant of RCC, which has an aggressive biologic behavior and poor prognosis, akin to sarcomatoid RCC. The current World Health Organization classification of RCC does not include the rhabdoid phenotype as a distinct histologic entity. The aim of this study is to investigate whether RCC-RM represents a dedifferentiation of a classifiable-type World Health Organization RCC or a carcinosarcoma with muscle differentiation. We reviewed 168 cases of RCC obtained between 2003 and 2008. From these cases, 10 (6%) were found to have areas of classic rhabdoid morphology. Immunohistochemistry for cytokeratin, epithelial membrane antigen, desmin, CD10, and CD117 was performed in each case using the labeled streptavidin-biotin method. Rhabdoid differentiation was identified in association with conventional-type RCC (9) and with unclassifiable-type RCC with spindle cell morphology (1). In all cases, both the rhabdoid and nonrhabdoid tumoral areas were positive for cytokeratin and epithelial membrane antigen and negative for desmin. Cytokeratin positivity in the rhabdoid areas was focal. In cases associated with conventional-type RCC, CD10 was positive in both the rhabdoid and nonrhabdoid foci. CD117 was negative in these tumors. The unclassifiable-type RCC with spindle cell morphology was negative for both CD10 and CD117. The similar immunophenotype between the rhabdoid and nonrhabdoid tumoral foci supports the origin of the rhabdoid cells from the classifiable-type RCC. Areas of rhabdoid morphology do not represent muscle metaplastic differentiation. Renal cell carcinoma with rhabdoid morphology may represent a dedifferentiation of a classifiable-type RCC, similar to that of sarcomatoid differentiation. The recognition of RCC-RM is important as it allows for the inclusion of these high-grade malignancies into a category associated with poor prognosis despite lacking the spindle cell component classically identified as sarcomatoid change

Examination of Genetic Aberrations in Chlamydophila Psittaci negative MALT Lymphomas of the Ocular Adnexa

Abstract Abstract 1569 Ocular adnexal mucosa associated lymphoid tissue lymphomas (OAMALTL) are the most common lymphomas of the eye. The etiology and pathogenesis of ocular adnexa MALT lymphomas (OAMALTL) are still unknown and the association with Chlamydophila psittaci (C. psittaci) has been shown in only some geographic regions. Only few small studies specifically examined for the presence of t(11;18)(q21;q21)/API2-MALT1, t(1;14)(p22;q32)/BCL10-IGH, t(14;18)(q32;q21)/IGH-MALT1, t(3;14)(p13;q32)/FOXP1-IGH translocations or for TNFAIP3 (A20) mutations/deletions, which may contribute to the activation of canonical nuclear factor (NF)-kB pathway in OAMALTL. Herein we sought to comprehensively examine the frequency of these translocations as well as CARD11 and MYD88 (L265P) mutations, in addition to A20 mutations /deletions in a large cohort of C. psittaci negative OAMALTL. A total of 47 OAMALTL originating in the orbit (22), conjunctiva (19) and lacrimal gland (6) were used for analysis. Dual color fusion probes for t(14;18)(q32;q21) IGH-MALT1, t(11;18)(q21;q21) BIRC3-MALT1 and dual color break apart probes for MALT1, BCL6, and CEP18 (chromosome 18 centromere) were used for FISH analysis in all the analyzed tumors. Dual color break apart probe for IGH was used for selected tumors. Extracted DNA was used for PCR amplification and sequencing of the coiled-coil domain of CARD11, exon 5 of MYD88, in which the L265P mutation was previously reported in diffuse large B-cell and MALT lymphomas, and all the coding exons of the A20 gene. A20 gene copy number variation was analyzed by TaqMan Copy Number Assay (Applied Biosystems). DNA extracted from peripheral blood lymphocytes of 3 healthy volunteers and OCI-LY8 and Jeko-1 cell lines served as calibrator and positive controls for A20 deletion. CARD11 mutations were not found in all the analyzed tumors. The MYD88 L265P mutation was detected in 3 (6.4%) tumors. A total of 9 A20 mutations were identified in 7 (14.9%) tumors. One tumor harbored 3 distinct mutations (F149C; 1bp deletion in exon 3 and 2bp deletion in exon 5). Among the 9 detected A20 mutations, the majority (89%) would produce truncated proteins due to out-frame insertion/deletion (7), while one of these deletions was located in a known splicing site. Only 2 missense mutations were observed, including one in a tumor in which 2 concomitant deletions were also present (described above). A20 heterozygous deletions were detected in 7 (14.9%) tumors. There was no association between A20 mutations and heterozygous deletion in any of the analyzed tumors. None of the tumors harbored a concomitant A20 mutation/deletion and MYD88 L265P mutation. A total of 5 tumors harbored chromosomal alterations: additional copy of BCL6, most probably due to trisomy 3, in 2 tumors, an additional copy of IGH in 1, extra copies of both IGH and MALT1 in 1, and extra copies of IGH, MALT1, BIRC3 together with IGH rearrangement to unidentified partner in 1. t(14;18)(q32;q21) IGH-MALT1 and t(11;18)(q21;q21) BIRC3-MALT1 were not detected in any of the analyzed tumors. A20 mutations were detected in a tumor with extra signals of both IGH and MALT1 genes as well as in one of the tumors with an additional copy of BCL6. The tumor with complex chromosomal aberrations including the IGH rearrangement to an unidentified partner also harbored A20 deletion. 26 of the analyzed tumors previously were shown to exhibit evidence of antigen selection based on the analysis of IGHV mutation pattern (PLoS One. 2011;6(12):e29114). There was no association between antigen selection and A20 mutations/deletions, MYD88 (L265P) mutation and chromosomal alterations. Overall, our data suggest that translocations characteristic for MALT lymphomas are rarely observed in OAMALTL. The MYD88 (L265P) mutation is also uncommon, while most of the A20 mutations/deletions affect only one allele and thus most probably do not lead to NF-kB activation. This raises a question on what are the mechanisms for canonical NF-kB signaling pathway activation in OAMALTL and if it is indeed activated in these tumors. It is possible that NF-kB signaling pathway activation maybe due to B cell receptor signaling, as may be reflected by association with presence of antigen selection that is observed in major fraction of these tumors. Immunohistochemical studies addressing these questions are underway and will be presented at the meeting. Disclosures: No relevant conflicts of interest to declare