ANNUAL MEETING ABSTRACTS 335A in oropharyngeal and oral cavity SCC. The further investigation of tumor-stromal-TILs 1342 B-Cell Lymphoma, Unclassifiable, With Features Intermediate interactions may provide a new insight into the immune response in head and neck SCC Between Diffuse Large B-Cell Lymphoma and Classical Hodgkin progression and future strategy for target treatment. Lymphoma – A Series of 24 Patients Tariq Aladily, Sanam Loghavi, L Jeffery Medeiros, Roberto Miranda. University of Texas MD Anderson Cancer Center, Houtson, TX; University of Jordan, Amman, Jordan. Hematopathology Background: B-cell lymphoma, unclassifiable, with features intermediate between diffuse large B-cell lymphoma (DLBCL) and classical Hodgkin lymphoma (CHL), also known as Gray zone lymphoma (GZL), is a rare disease that has been recently 1340 Clinicopathologic and Next Generation Sequencing Analysis of included in the WHO classification of tumors of hematopoietic and lymphoid tissues. Follicular Dendritic Cell Sarcomas Only few cases are available in the literature. Anmaar Abdul-Nabi, Catherine Cottrell, Chad Storer, Friederike Kreisel, TuDung Design: We reviewed cases of GZL between 2000 and 2013 and extracted clinical Nguyen. Washington University, St. Louis, MO. and pathologic features. Background: Follicular dendritic cell sarcoma (FDCS) is an uncommon malignancy Results: A total of 24 cases were identified. The median age at the time of diagnosis characterized by a proliferation of spindled to ovoid cells with morphology was 39 years (range 20-64). 13 patients were men and 11 were women (M:F 1.18). and immunophenotype characteristic of follicular dendritic cells. Although the Mediastinum was the most common site: 18/24 (75%), followed by neck lymph nodes: clinicopathologic features of these rare tumors have been extensively studied, specific 17/24 (71%). Clinical stage was as the following; stage II: 13/21 (62%), stage III: 5/21 gene mutations or chromosomal alterations associated with FDCSs are largely unknown. (24%), stage IV: 3/21 (14%), while none had stage I disease. Histopathologically, four Design: We retrospectively identified 11 FDCSs diagnosed at our institution between patterns were identified according to the morphologic and immunophenotypic profiles. 2001 to 2014. The clinicopathologic features for these cases were collected from the Cases with the morphology of CHL but immunophenotype of DLBCL were the most clinical databases, along with treatment, overall survival, and follow-up data. 3 cases common and attained better outcome than other subtypes. Complex cytogenetic with available tissue underwent targeted next generation sequencing (NGS) analysis aberrations were found in all tested cases. Chemotherapy (CT) was given to all patients, by a hybrid-capture approach to evaluate the coding region of 151 cancer-associated radiotherapy (RT) to 9/22 (41%) and stem cell transplant (SCT) to 6/22 (27%). The genes. Variants were called by VarScan 2.3.6, and following review, were categorized median event free survival was 9 months (range 0-54), while the median overall survival as clinically actionable, uncertain significance or benign, the latter used if they were was 30 months (range 7-62). The rate of complete remission was 11/20 (52%), but polymorphic. relapse rate was common: 7/11 (64%), which occurred at a median interval of 15 months Results: The 11 FDCS cases presented at a median age of 51 years (range 28-71) with (range 5-24). Both regimens commonly used for the treatment of Hodgkin lymphoma a 2.6 male: female ratio. The mean follow-up was 26.4 months (range 1-115). The and non-Hodgkin lymphoma attained similar results in our patients. sites involved at diagnosis included: liver, spleen, mediastinum, neck, lymph node, Conclusions: GZL represents a distinct type of lymphoma. Women were more pharynx, rectum, and peritoneum. The tumors showed classic morphology of a FDCS, commonly affected in this series. Treatment with standard regimens for CHL and and all were CD21+ and/or CD35+. All but 2 cases did not recur/metastasize after DLBCL would obtain inferior results in GZL. Intensive CT, consolidation RT, SCT treatment by surgery, radiation and/or chemotherapy. Targeted NGS revealed 2 to 6 and targeted therapy would improve the outcome. novel non-synonymous coding (NSC) sequence variants per case predicted to modify protein function. Although the 3 cases shared no mutual NSC mutations, the impacted pathways/proteins included a receptor tyrosine kinase, PI3K signaling, and G-protein 1343 Large Granular Lymphocytic Leukemia (LGL): A Detailed signaling. One case had a well-known PI3K pathway mutation documented in other Clinicopathologic Analysis With Focus on STAT3 Expression Profile cancers that is amenable to mTOR inhibitor therapy. Mustafa Al-Kawaaz, Marcello Gaudiano, Ghaith Abu-Zeinah, Jia Ruan, Attilio Orazi, Conclusions: The FDCS in our cohort exhibited similar histopathologic and clinical Wayne Tam, Giorgio Inghirami, Julia Geyer. Weill Cornell Medical College, New features to that of other published series. The molecular landscape of these tumors York, NY. varied, and the affected genes differed among the 3 cases. A targeted NGS approach Background: LGL is an indolent chronic lymphoproliferative disorder characterized by for these rare tumors has clinical utility, revealing alterations in established signaling expansion of clonal T or NK cells. LGL is frequently associated with chronic immune pathways, and identifying somatic mutations with known therapeutic implications. stimulation. Transient oligoclonal and monoclonal populations are very common Future analysis of additional cases will help to determine common biological pathways and are difficult to distinguish from true malignancy. Diagnostic criteria for LGL are which may be targets for new therapies. controversial and are not well-defined. Recent studies have identified somatic STAT3 mutation in ∼40% of LGL. It is unclear if the constitutive activation of the JAK/STAT3 pathway correlates with the presence of somatic mutation in LGL. The purpose of this 1341 The Inhibitor of NF- B Kinase, IKK , Regulates the Stability of the κ β study was to clinically validate use of STAT3 antibody in a cohort of well-defined LGLs. Hedgehog Transcription Factor GLI1 Design: Thirty five patients diagnosed with LGL using strict WHO classification Nitin Agarwal, Chae Hwa Kim, Kranthi Kunkalla, Francisco Vega. University of Miami, criteria and presence of monoclonal TCR gene rearrangement were selected. Sylvester Cancer Center, Miami, FL. Immunohistochemical (IHC) staining for CD3, CD8, CD56, cMYC and pSTAT3 Background: Constitutive activation of the Hedgehog (Hh) transcription factor, GLI1, was performed. The region of exon 21 within the SH2 domain of STAT3 gene was has been demonstrated in many cancers including diffuse large B-cell lymphoma interrogated by PCR-Sanger sequencing. (DLBCL). Hh signaling provides survival signals to DLBCL cells. The mechanisms Results: There were 15 men and 19 women with mean age of 61 (27-84) years. Patients controlling GLI1 transcriptional activity are poorly characterized. Herein, we show that presented with anemia (22), neutropenia (16) and/or thrombocytopenia (12). Mean PB the inhibitor of NF-κB kinase, IKKβ, interacts, phosphorylates and stabilizes GLI1. LGL count was 3.5 x 103/ul. Sixteen (47 %) patients had an associated viral infection Design: To identify regulatory components that participate in the transcriptional activity or autoimmune disease. Nineteen (56 %) had a concomitant hematologic malignancy. of GLI1, we explored GLI1 putative interacting proteins by liquid chromatography Twelve (34%) patients required treatment. Positive IHC staining for pSTAT3 was seen tandem mass spectrometry following immunoprecipitation (IP) of endogenous GLI1. in 6 (18 %) patients: 4 were previously healthy and 2 had another malignancy. pSTAT3 The binding between IKKβ and GLI1 was confirmed by IP assays. The role of IKKβ was negative in all patients with associated viral infection or autoimmune disease. in blocking degradation of GLI1 was assessed by a set of experiments including IHC staining for cMYC was seen in 11 (32%) cases and positively correlated with transfection studies, pharmarcological inhibition and knocking down of GLI1. To pSTAT3 IHC. There was no statistical correlation between IHC pSTAT3/MYC status identify IKKβ-dependent GLI1 phosphorylation sites, we co-transfected full length GLI1 and patient’s age, sex, cytopenia or need for therapy. No detectable oncogenic STAT3 and IKKβ constructs in 293T cells and the IKKβ-GLI1 complex was purified. Peptides (Y640F) mutations were identified. resulting from digestion of GLI1 were analyzed by mass spectrometry. Mutational Conclusions: LGL presents a diagnostic challenge due to lack of reliable markers. studies were also performed to assess the role of the identified IKKβ -mediated Contrary to previous reports, we did not detect proven oncogenic STAT3 mutations phosphorylated sites in GLI1 stability. These studies were performed on DLBCL cell in a series of carefully selected, well-characterized cases of LGL. IHC pSTAT3 was lines (SUDHL4, DOHH2, OCI-Ly19, HBL-1) and 293T cells. seen in 6 (18%) cases. These patients may represent a unique group, since they had no Results: GLI1 was found to be associated with full length IKKβ, but not with the documented associated inflammatory disorder. There was a trend for increased symptom kinase-dead IKKβ mutant (K44A). Short stimulation of DLBCL cells (SUDHL4