ECP 2023 Abstracts

S318 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 E-PS-15-050 Implementation of a Next Generation Sequencing (NGS) service for cfTNA analysis to facilitate driver mutation reporting in blood R. Werner*, R. Crosbie, M. Dorney, J. McCarthy, C.K. Hand, L. Burke *Pathology Department, Cork University Hospital, Cork, Ireland, Department of Pathology, School of Medicine, University College Cork, Cork, Ireland, Ireland Background & objectives: The establishment of a cfTNA (cell-free- Total Nucleic Acid) NGS service integrated within an ISO15189- accredited clinical diagnostic NGS laboratory in a designated tertiary cancer centre. This is an emerging clinical tool with rapidly expanding utility as cost reduces and sensitivity/specificity improve. Methods: Validation was performed on the Genexus™ utilising Oncomine™, a targeted NGS panel on cfTNA extracted from plasma. Oncomine Reporter™ software was used to report on variants, and fusions across >42 key genes. Plasma verification samples with known driver mutations in matched tissue biopsies were utilised. Assessment criteria included sensitivity, specificity, limit of detection, reproduc- ibility, and the establishment of performance metrics. Results: Performance metrics and quality parameters established. Sensitivity between plasma and tissue of >83%, Sensitivity between plasma and plasma NGS or cfDNA orthogonal methods of 100%. Variant specificity of 100% across all methods. TNA extraction and purification was optimised on the Genexus Puri- fication Instrument and sequencing performance established with an accepted LOD of 1.2% when depth of coverage of >22,000 was reached. Allelic frequency of NSCLC tier I variants did detect as low as 0.6%. Stability of plasma samples from EDTA blood tubes established with >90% of the verification samples in prolonged storage at -80°C for >12 months. Turnaround times (TAT) of cfTNA results to Oncologists reduced by >50% to date. Conclusion: Successful implementation and clinical validation of a fully automated novel cfTNA NGS workflow was achieved. Optimi- sation of Oncomine Reporter software to streamline NGS on cfTNA without in-house bioinformatics expertise. The average TAT from reference laboratories with expertise in sequenc- ing cfTNA are typically >3 weeks; prolonged TAT for biomarker anal- ysis can adversely affect patient outcomes. Significant reduction in TAT of cfTNA NGS results has not yet been achieved in any diagnostic pathology laboratory in Ireland. E-PS-15-051 Spectrum of mutations in homologous recombination repair genes in metastatic hormone-sensitive prostate cancer V. Zakharava*, D. Balshakova, M. Smal, R. Goncharova, A. Murad- khanau, Y. Poddubny, A. Rolevich, S. Krasny *N.N.Alexandrov National Cancer Centre of Belarus, Belarus Background & objectives: Mutations in homologous recombination repair genes increase the risk of prostate cancer, as well associated with poor prognosis and response to systemic therapy. Objective was to study germline mutations in DNA repair genes in metastatic hormone-sensitive prostate cancer (mHSPC). Methods: Genetic study of mHSPC patient specimens (n=40) was performed using high-throughput targeted sequencing platforms and included the detection of mutations in the BRCA1, BRCA2, ATM, CHEK2 and PALB2 genes. ISUP Grade varied from 2 to 5, with predominant of GG4-27.5% and GG5-41.25%. Multiple and solitary metastases were observed in 96.1% and 3.9% of patients; regional lymph node involvement in 70%. Results: In group of patients with mHSPC twenty-four mutations (10 in introns, 14 in exons) were found. The frequency of germinal mutations in patients was: BRCA1-12.8%, BRCA2-35.9%, ATM-12.8%, of which pathogenic variants were 5.1%. The identified variants included: 2 pathogenic mutations, 4 of indeterminate clinical significance, and 18 benign/probably benign. Analysis of polymorphic variants of BRCA2, BRCA1, and ATM revealed 23 single-nucleotide substitutions (13 mis- sense and 10 synonymous variants). Two mutations (5.1%, including 1 pathogenic variant) were detected in the CHEK2 gene, five mutations (12.8%, including 2 pathogenic variant) in the PALB2 gene, and one mutation in the AR gene (2.6%). Conclusion: The frequency and spectrum of mutations in the BRCA1, BRCA2, ATM, CHEK2 and PALB2 genes using high-throughput tar- geted sequencing in patients with mHSPC were shown. The pathogenic frameshift deletion c.4035del, which is causal in breast and ovarian cancer, was detected. A rare in the population single nucleotide substi- tution rs28897688 was found in 5.13% of patients with mHSPC, which may indicate its risk significance for mHSPC. E-PS-16 | E-Posters Nephropathology E-PS-16-001 Membranous nephropathy associated with monoclonal gammopa- thies: case series M.L. Abascal Camacho*, C. Vieru, Y. Gómez Navarro, Ú. Verdalles Guzman, T. Bada Bosch, J.C. De la flor, F. Arias, M. Goicoechea Diezhandino., F.J. Díaz Crespo *Hospital General Universitario Gregorio Marañón, Spain Background & objectives: Membranous glomerulonephritis (MGN) is a common cause of nephrotic syndrome, characterized by subepi- thelial polyclonal immune-complexes deposits along glomerular base- ment membrane. MGN pattern with or without monoclonal deposits associated to monoclonal gammopathies is a rare entity with few cases reported. Methods: A retrospective analysis was perform on renal biopsy samples received between 2019-2023, identified 4 cases of MGN, 3 with mono- typic deposits. Light microcopy, immunochemistry-immunofluorescence and electron microscopy were performed. The average age of diagnosis was 62 years, with female predominance. Two patients had a lymphopro- liferative disorder (Marginal zone lymphoma (LMZ) and LLC-B)), and two monoclonal gammopathy of renal significance (MGRS). Results: Patients with lymphoma demonstrated a mean serum cre- atinine of 1,45mg/dl, proteinuria 4g/24h and Kappa/lambda ratio 19. Conversely, MGRS cases had mean serum creatinine 1,21mg/ dl, proteinuria 2,16g/24h, Kappa/lambda. Renal biopsies showed diffuse thickening of capillary walls and silver positive “spikes” without evidence of endocapillary proliferation or crescents. One case showed infiltration of LM (40%) and LLC patient showed scattered interstitial monotypic plasma cells. Immunofluores- cence revealed IgG and C3 granular deposits in capillary wall in 100% cases C1q++ in 2 cases and IgM+++ in one. 75% of cases presented light-chain restriction (3 kappa/1 lambda). PLA2R was negative in serum and by immunochemistry. Electron microscopy evidenced amorphus subepithelial electron-dense deposits in all cases. Conclusion: MGN pattern associated to monoclonal gammopa- thies is an extremely rare and heterogenous group. All cases with monotypic deposits coincide with monoclonal component and sowed remission after clone-targeted therapy. IgG-subclass stain- ing could be useful to clarify the light chain restriction. Despite not being recognized as a histological pattern within monoclonal gammpopathies, it may be worthwhile consider it. The diagnosis of this entity require careful evaluation of renal biopsy specimens using a combination of light microscopy, immunofluorescence and electron microscopy.