ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 Conclusion: Despite an intense dependence of GCBCs on OXPHOS, glycolysis is a significant energy supporter too. Tissue in situ analysis suggests the coupling of massive division in DZ with OXPHOS and local exchange of lactate, while glycolysis is more frequent among B cells in LZ. Moreover, the lactate transporters’ expression and the impaired Krebs cycle capacity induced by MPC-blockade point to a significant role of glucose-derived carbon atoms and monocarboxylates in sustaining the oxidative machinery. OFP-12-011 Comparison of the accuracy of cytomorphology, f low cytometry immunophenotyping and immunohistochemistry in determining diagnostic and prognostic blast percentage groups in bone marrow in myelodysplastic syndrome and acute myeloid leukaemia cases E. Hacihasanoglu* *Yeditepe University, Turkey Background & objectives: Bone marrow (BM) blast percentage (BP) is important in diagnosis, classification and prognosis of myelodysplastic syndrome (MDS) and acute myeloid leukaemia (AML). We aimed to compare accuracy of cytomorphology (CM), flow cytometry immunophenotyping (FCI), immunohistochemistry (IHC) in determining BP groups. Methods: BM biopsy and aspiration samples from MDS and AML patients and patients diagnosed with AML underwent bone marrow transplantation (BMT) between 9/2019 and 6/2021 were analysed. CM was evaluated. CD34 positive BP was determined by FCI and IHC. Cases were divided into four groups according to BP: <5%, ≥5%-<10%, ≥10%-<20%, ≥20%. Three methods were compared with the Pearson-r correlation. Results: A total of 68 BM materials from 55 patients were analysed. Thirty-nine of the cases were MDS (7 MDS-EB), 2 of them were AML, and 14 of them were AML patients who underwent BMT. Pearson-r correlations for absolute values in CM-FCI, CM-IHC, and FCI-IHC comparisons were 0.8865, 0.8787, 0.9670, respectively, indicating a good correlation. When CM-FCI was compared, 86.7% of the cases were in the same blast range. In the comparison of CM-IHC, 79.4% of the cases were in the same blast range. Comparison of IHC-FCI showed 88.2% correlation in blast intervals. Conclusion: BM blast rate determination is important in MDS classification and MDS-AML differentiation. Although CM is the gold standard, reproducibility is low even with high-quality smears. In our study, we observed good correlations between CM, FCI and IHC. Correlation between FCI and IHC, which have high reproducibility and low interobserver variability, was even higher. However, this study is limited to cases showing CD34 expression. Although FCI and IHC methods have high accuracy with CM, using the three methods together is recommended. OFP-12-012 Prevalence and impact of co-infections in patients with lym- phoma and HIV C. Padrão*, A.M. Gonçalves Pereira, F. Pereira, J. Tinoco, M.G. Gasparinho *Hospital Prof. Dr. Fernando Fonseca, Portugal Background & objectives: HIV infection is associated with the development of lymphomas and some other co-infections (eg., HBV and HCV). The aim of our study was to review lymphomas arising in HIV setting and linked co-infections, in a patient’s cohort from our hospital. Methods: We selected patients diagnosed with HIV and lymphoma between 2010-2020 in our hospital, from our electronic medical database. Demographic data, date of diagnosis, date of death/last contact, lymphomas types and location, serologies for hepatitis B and C, cytomegalovirus, toxoplasma and Epstein-Barr virus (6 months prior until 3 months after lymphoma diagnosis) were col- lected. Descriptive statistical analysis was performed. Results: We selected 52 patients (71.2% males). HIV-1 was pre- dominant (90.4% of the cases). Average age of HIV diagnosis was 42.38 years and of lymphoma diagnosis was 47.79 years; mean interval between diagnoses was 64 months (36.5% diagnosed within 1-year). Laboratory data demonstrated high prevalence of chronic hepatitis C (9.6%) and B (28,8%) and low prevalence of recent EBV (1.9) or CMV (3.8) infection. Diffuse large B cell lymphoma (40.4%), Hodgkin’s lymphoma (23.1%) and plasmablastic lymphoma (11.5%) were the most frequent types. Lymph node involvement (59.6%) was predominant, followed by bone marrow (7.9%) and gastric involvement (5.8%). Mortality rate was 59.6%. Median survival was 11.71 months after lymphoma diagnosis. Conclusion: Our patients’ cohort follows the general patterns of gender, HIV type distribution and main types of lymphomas diag- nosed in HIV-infection setting usually described in literature. We have a higher frequency of plasmablastic lymphoma though, not readily explained by a similar rise of frequency of EBV infection – not all patients were tested for EBV, what may account for the lower frequency observed. We hope to further investigate this point in future studies. OFP-13 | Joint Oral Free Paper Session Neuropathology / Oph- thalmic Pathology OFP-13-001 Immunohistochemistry against RB1 is useful for the distinction between giant cell glioblastoma and pleomorphic xanthoastrocytoma V. Barresi*, S. Michele, C. Ciaparrone, S. Pedron, A. Mafficini, A. Scarpa *Department of Diagnostic and Public Health, University of Verona, Italy Background & objectives: Giant cell glioblastoma (GC-GBM) displays frequent RB1 alterations, aside from TP53 mutations. Herein, we aimed to assess the value of RB1 immunohistochemistry in the differential diagnosis between GC-GBM and pleomorphic xanthoastrocytoma (PXA), which harbours better prognosis and frequent BRAF mutations. Methods: In 34 GC-GBMs and 8 PXA (5 grade 2 and 3 grade 3), we analysed: i) mutations and copy number variations of 409 genes using NGS; ii) RB1, P53 and BRAF p.V600E immunostain- ings. Cases were classified P53 positive when showing at least 10% stained tumour cells. Results: GC-GBMs were RB1-altered in 15 cases (including 4 with RB1 homozygous deletion, 5 with RB1 heterozygous deletion coupled with mutation of the other allele and 6 with RB1 muta- tions), TP53-mutated in 27 (including 6 with truncating mutations) and BRAF-mutated in none. At immunohistochemistry, all 15 GC- GBMs with RB1-alterations and 11 RB1-unaltered cases had RB1 loss, 21 were P53 positive and all were BRAF negative. GC-GBMs were RB1-/P53+ in 16 cases, RB1-/P53- in 10, RB1+/P53+ in 5, RB1+/P53- in 3. S52