ECP 2023 Abstracts

S277 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 EBV(-)-DLBCL on the response to R-CHOP treatment (p=0.01) and survival rate between the two groups. Log Rank (Mantel-Cox) p=0.0001. Conclusion: We suggest that regulation of EBV-induced immunosup- pression by inhibiting PD-1 and its ligands may improve immuno- therapy outcomes. E-PS-11-029 Expression of IL-6 in Epstein–Barr virus-positive diffuse large B-cell lymphoma, a potential targeted therapy and cell signalling N. Moulai*, R. Bennoui, M. Guermi, W. Ouahioune *Faculty of Medicine of Blida, Algeria Background & objectives: Epstein–Barr virus-positive (EBV+) dif- fuse large B-cell lymphoma not otherwise specified (DLBCL NOS) is an aggressive clinicopathological entity associated with a poor prog- nosis. The IL-6/JAK/STAT3 signalling pathway is aberrantly hyperac- tivated in patients with haematopoietic malignancies or solid tumours. Methods: We evaluated the expression of IL-6 (10C12) using an H-score, STAT3 Thyr705 (13-7) with 40% of cut-off, and NF- қ B P50 (polyclonal) by immunohistochemistry in 78 EBV-DLBCL including 67 with ABC and 11 GCB and 13 EBV+DLBCL ABC phenotype. We compared the expression on the microenvironment (ME) and lymphoid tumour cells. Results: In our study, a significant difference in IL-6 expression was found between the EBV+DLBCL and EBV-DLBCL p=0.002. How- ever, its expression was noted mainly by lymphoid tumour cells and ME in the EBV+ DLBCL and only by the ME of the EBV-DLBCL. The Pearson test showed a significant correlation between the expres- sion of IL-6 and STAT3 (r=0.368, p=<0.000) and between the expres- sion of IL-6 and NF-κB P 50 (r=0.272, p=0.009). Conclusion: We suggest that the IL-6 signalling pathway has a key role in the lymphomagenesis of EBV+ DLBCL. IL-6 expression by lymphoid tumour cells and ME cells would activate the transcription factors STAT3 and NF- қ B P50. This leads to new therapy perspectives. E-PS-11-030 Gastrointestinal follicular lymphoma: comprehensive clinicopatho- logical review of 22 cases and diagnosis classification K. Na*, C.H. Oh, H. Kim, S. Do *Department of Pathology, Kyung Hee University Hospital, Kyung Hee University College of Medicine, Republic of Korea Background & objectives: Duodenal type follicular lymphoma (DFL) and classic follicular lymphoma (CFL) are important differential diagnosis of gastrointestinal follicular lymphoma (GIFL). This study describes an integrated diagnostic process of GIFL and identifies useful features for the differential diagnosis. Methods: We thoroughly reviewed clinicopathological features of 22 patients with GIFL, providing long follow up data and lymph node (LN) status. Following WHO classification, the cases were classified into DFL or CFL. Some undetermined cases were initially classified as GIFL, not otherwise specified (NOS) and their diagnosis was further classified with integration of overall clinicopathological features. Results: Thirteen cases in duodenum showing grade 1 histological feature and the absence of LN involvement were classified as DFL. Five cases in non-duodenal location showing either grade 3 histological feature or LN involvement were classified as CFL. Endoscopic find- ing of CFL was overt mass forming lesion, in contrast to tiny nodules observed in DFL. CD21 expression in neoplastic follicles of DFL was predominantly or completely peripheral, whereas that those in CFL was strong and homogeneous. Four cases of GIFL, NOS were fur- ther categorized into 3 CFL of duodenum, stomach and colon, and 1 colonic DFL. Of these 4 cases, LN involvement was detected in CFL of duodenum and colon. Conclusion: Our study supports that clinicopathological features of DFL are largely different from CFL. Routine LN evaluation may not be mandatory for patients with typical case of DFL. In cases of GIFL showing unusual features for DFL, the possibility of GI involvement of CFL should be considered and the presence of LN involvement should be carefully evaluated. In addition to endoscopic findings and histopathological features, CD21 expression pattern can assist in the differential diagnosis between DFL and CFL. Funding: This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning (2020R1G1A1003692). E-PS-11-031 MiR-125b and miR-155b and their relationship with MYC, BCL2 and TP53 in diffuse large B-cell lymphoma E. Neves Filho*, S. Zancheta, S.H. Rabenhorst *LABGEM, Brazil Background & objectives: Tumoral microRNAs, such as miR-125b and miR-155b, are important gene expression regulators with complex pathogenetic mechanisms. However, their role in DLBCL, especially when other biomarkers and cell-of-origin classification are considered, are still to be elucidated. Methods: In a series of 139 DLBCL cases considering germinal centre (GC) versus nonGC subtypes according to Hans algorithm, we investi- gated miR-125b and miR-155b expression by in situ hibridization and their association with some immunophenotypic presentations, includ- ing MYC, BCL2 and TP53 expression by immunohistochemistry and MYC, BCL2 and BCL6 translocation status by FISH. Results: miR-125b was detected in 58.5% and miR-155b in only 24.4% of the studied cases. In the nGC patients, miR-125b detection was posi- tively correlated to the Ki-67 index (p= 0.035). Considering the GC subgroup, besides a miR-125b association to Ki-67>70% (p= 0.043), the percentage of miR-125b positive cells was also correlated to either MYC and MYC/BCL2 double expression (p= 0.047 and p= 0.049, respectively). No associations were observed between miR-125b and the studied chromosomic rearrangements, nor between miR-155b and any of these parameters. Conclusion: In conclusion, miR-125b is associated to high proliferation index independently on cell-of-origin subtypes and a pathway involving miR-125b and MYC seems to be a GC characteristic. Funding: This work was supported by the Fundação Cearense de Apoio ao Desenvolvimento Científico e Tecnológico (FUNCAP) [PPSUS 2017]. E-PS-11-032 Gastric mastocytosis: an underdiagnosed and rare entity N. Oza*, V. Anandaswamy, S. Gujral, F. Ahmed, S. Kane *HISTOPIA LAB, India Background & objectives: Mastocytosis is rare heterogeneous group of neoplastic mast cell disorders. The disease is divided into pure cuta- neous and systemic disease with over 90% cases exhibiting D816V KIT mutation. Gastric mastocytosis poses a challenging diagnosis and represents major cause of morbidity. Methods: An elderly male with clinical suspicion of lymphoprolifera- tive disorder presented with abdominal pain and vomiting. Imaging revealed circumferential thickening of gastric and D1/D2 wall; while endoscopy revealed oedematous hyperemic gastric and D1 mucosa. Histopathologic evaluation of gastric biopsy revealed mast cell neo- plasm which was further confirmed by Sanger sequencing and serum tryptase levels. Results: A gastric biopsy of 67-year-old male with oedematous gastric mucosa on endoscopy revealed antral type of gastric mucosa with lam- ina propria showing mast cells arranged in sheets. These show round to ovoid nuclei with vesicular chromatin and pale eosinophilic cytoplasm. By Immunohistochemistry, the mast cells showed diffuse positivity for