ECP 2023 Abstracts

S276 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 E-PS-11-025 A case of acute monoblastic leukaemia in adult patient P. Kasparova*, K. Rudolf, A. Sykorova *The Fingerland Department of Pathology, Charles University, Fac- ulty of Medicine in Hradec Králové and University Hospital Hradec Králové, Czech Republic Background & objectives: Acute monoblastic/monocytic leukaemia is one of the most common subtypes of Acute Myeloid Leukaemia (AML) in children. Patients with AMoL often exhibit hyperleuko- cytosis, disseminated intravascular coagulation, and extramedullary involvement, particularly in the skin, gingiva, and central nervous system (CNS). Methods: We report a case of adult patient (62 years old) presenting with ascites and clinical suspicion of acute pancreatitis. Than the dif- fuse infiltration of stomach wall was found, suspected of poorly cohe- sive type of gastric carcinoma. The biopsy was done, and the leukemic infiltration was found. Afterward the diagnosis of AMol was set from the trephine biopsy specimen. Results: During the diagnostic process cytology was done at first, from the ascites, with finding of population of histiocytic cells, but due to the clinical data it was interpreted as reactive, „cleaning“ reaction to pancreatitis. When the biopsy from the stomach mucosa was exami- nated with the finding of leukemic infiltration of monocytic/mono- blastic type, the cytologic report was revised to leukemic infiltration. Because of the finding of extramedullary leukemic infiltration, the bone marrow examination was suggested. In the trephine biopsy specimen massive leukemic infiltration was found as well. Conclusion: Our case represents quite typical problems of diagnostic process of AMoL in adult patients – due to other more typical diag- nosis and causes of the effusions could be the right diagnosis missed for some time. But although AMoL is more typical for children, we can find in adult patients as well, with rather common extramedullary infiltration and especially malignant effusions. That´s why we should have the possibility of AMoL in the differential diagnostic scheme in adult patients as well. E-PS-11-026 A rare case of jejunal plasmacytoma presenting with small bowel stricture C. Kwon*, K. Davidson, M. Rahilly *NHS Lothian, United Kingdom Background & objectives: The gastrointestinal tract is a rare site for extramedullary plasmacytoma (EMP), an uncommon tumour. We pre- sent an unusual case of a solitary jejunal plasmacytoma in a 33-year-old male who presented with subacute jejunal obstruction, and discuss the clinical implications. Methods: In addition to the patient’s notes, the literature was reviewed utilising Google Scholar, Pubmed and WHO Blue Books references. Results: A 33 year-old man presented with intermittent abdominal pain and vomiting. CT scanning demonstrated a jejunal obstruction with local mesenteric lymphadenopathy. The strictured jejunum was resected at laparotomy. Histopathology showed a 16mm submucosal nodule at the stricture. The nodule was composed of solid sheets of CD138 positive lambda light chain restricted mature appearing plasma cells. The cells were negative for Cyclin D1, CD56, pan-cytokeratins and neuroendocrine markers. Local nodes were negative for tumour. Para-protein, serum free light chain ratio and a skeletal survey were negative. Bone marrow aspirate and trephine were negative for plasma cell neoplasia. The features were interpreted as a plasma cell neoplasm based in the jejunal wall. Conclusion: EMP is a localised monoclonal plasma cell neoplasm that is rarely found in the jejunum[1]. We discuss EMP of the jejunum and the differential diagnosis of localised marginal zone lymphoma with extreme plasmacytic differentiation. The patient is well and awaits radical radiotherapy. E-PS-11-027 Immunomorphological characteristics of diffuse large B-cell lym- phomas - a quaternary care centre experience A. Lakshmanan*, N. Mulchandani, A. Ravichandran, A. Subramanyam *Apollo Hospitals, India Background & objectives: Diffuse large B-cell lymphomas (DLBCL) are the commonest aggressive B-cell non-Hodgkin Lymphomas world- wide. Their subclassification is challenging due to overlapping histo- pathological, immunophenotypical and genetic characteristics. This is reflected by the WHO classification of DLBCL into many variants and specific entities. Methods: All cases of DLBCL that were diagnosed during the period of 2017-2019 were retrieved and analysed. Immunohistochemistry (IHC) was done on all the cases. The cell of origin (COO) subtyping was done using Hans algorithm. A cut-off of 40% for C -MYC and 50% for BCL2 and BCL6 has been applied to assess the expressor pattern. Results: A total of 395 cases of DLBCL were diagnosed over the study period. The mean age at diagnosis was 57.2 years (12-95 years). A male predominance was noted with a male to female ratio of 2:1. Nearly half of the cases had primary extra nodal presentation. The mean proliferation index as assessed by Ki67 was 74%. The morphology had predominant centroblastic features (72.9%) followed by anaplastic (15.7%) and immu- noblastic features (6.3%). 5.1% of the cases had blastoid morphology. They were predominantly non-germinal centre B cell type (55%). The double expressor and triple expressor phenotypes were seen in 11.4% and 17.2% cases respectively. Isolated c-MYC expression was noted in 6.6% cases. Conclusion: DLBCL is a heterogeneous disease with numerous enti- ties. Molecular studies play a substantial role in diagnosing few of these specific entities as well as in prognostication. Although there are no strict recommendations in how to choose cases for FISH analysis or other molecular studies, morphological and IHC findings are invaluable to assess various prognostic factors such as COO determination and expressor patterns especially in resource limited countries. E-PS-11-028 Comparison of the expression of regulatory T cells transcription factor FOXP3 and PD1 in the tumour microenvironment of EBV+ and EBV- diffuse large B-cell lymphoma NOS N. Moulai*, R. Bennoui, M. Guermi, W. Ouahioune *Faculty of Medicine of Blida, Algeria Background & objectives: There is little information about the possible role of Tregs in EBV+ DLBCL NOS. We aim to determine the contri- bution of the immunomodulator microenvironment and its relationship with the immune checkpoints, by the expression of Foxp3, and PD-1. Methods: We evaluated the expression of FOXP3 (236A/E 7) using an H-Score and PD1 (NAT 105) by immunohistochemistry in 78 EBV- DLBCL including 67 with ABC and 11 GCB and 13 EBV+DLBCL ABC phenotype. We compared their expression on the microenvironment (ME). Results: The Mann-Whitney test showed no significant difference for FOXP3 (p=0.06) between the two groups. Our results showed a signifi- cant difference. The PD1 expression in the microenvironment of EBV+ DLBCL and EBV- DLBCL was significantly different p=<0.0001. Pear- son’s test showed a significant correlation between PD-1 expression and FOXP3 (r=0.56, p=<0.0001) with linear regression. Our results showed a significant difference between the two groups EBV(+)-DLBCL and