ECP 2023 Abstracts

S314 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 E-PS-15-036 Histopathological and molecular spectrum of KRAS- mutant non- small cell lung carcinoma (NSCLC): Indian tertiary cancer centre experience T. Pai*, S. Dash, M. Gurav, P. Gogte, N. Karnik, P. Shah, R. Kumar, A.K. Singh, O. Shetty *Department of Pathology, Tata Memorial Hospital, Parel, India Background & objectives: KRAS mutant NSCLC indicate an overall poorer survival compared to KRAS wild-type tumours. The approval of direct KRAS G12C inhibitor, sotorasib, mandates the need to identify these mutations. We present the spectrum of KRAS mutations among the Indian NSCLC patients. Methods: This is a retrospective analysis of NSCLC subjected to NGS on FFPE tumour samples between 2019 to 2022 using Ampliseq Focus and Sophia Solid Tumour Plus Solution. The data analysis was performed using Base space software for Ampliseq Panel and Sophia DDM platform for STS Plus. The analysis and interpretations were done as per the AMP and CAP guidelines. Results: KRAS mutations were seen in 59 cases. Age range: 23-89 years. 16 (27%) were female patients. Majority cases were histologi- cally adenocarcinoma, ( 88%), one each of SCC and NSCLC, NOS, with the rest were poorly differentiated carcinoma. Mucinous histology was noted in 7 cases. Most common KRAS mutations were G12C & G12D (n=19 each, 32%) & G12V (n=12, 20%). Others: Q61H (n=4), G12A (n=3), and one each of G12R and K117N. Concurrent muta- tions were seen in 44%, most commonly with p53 mutations (69%). PDL1 (SP263 Ventana clone) was negative in 23 cases (39%), while was ≥50% in 12 cases (20%). EGFR and CDK4 gene amplifications were seen in 1 case each. Conclusion: The present study unravels the diverse spectrum of KRAS mutations seen in Indian population, with G12C & G12D being the most common mutant variants. Histologically adeno- carcinoma is the most common histological subtype, followed by cases exhibiting poorly differentiated/ undifferentiated/ sarcomatoid morphology. With the novel KRAS inhibitors, it is important to ascertain the exact mutant variant to determine the eligibility to the targeted therapy. E-PS-15-037 VHL pathogenic variants in a series of Russian patients with clini- cal signs of von Hippel-Lindau disease G. Raskin*, G. Yanus, E. Suspitsin, Y. Gorgul, S. Aleksakhina, E. Imyanitov *Dr. Berezin Medical Insitute, Russia Background & objectives: von Hippel-Lindau disease is a hereditary tumour syndrome, caused by VHL mutations, and presenting with renal cysts and clear cell kidney cancer, hemangioblastomas, pheochromo- cytomas, etc. Methods: The study included 19 unrelated Russian patients (age range: 16-56 years, mean: 35,3 years). Clear cell renal cancer was diagnosed in 14/19 (74%) subjects, hemangioblastomas were identified in 5/19 (26%) cases, pheochromocytomas were found in 4/19 (21%) indi- viduals. VHL (NM_000551) coding sequence was analysed by HRM/ Sanger sequencing. Large gene rearrangements (LGRs) involving VHL were assessed by droplet digital PCR. Results: VHL PVs were identified in 6/19 (32%) patients. There were 4 known pathogenic/likely pathogenic nucleotid substitutions (c.463+2T>G, c.491A>G (p.Gln164Arg), c.499C>T (p.Arg167Trp), c.641G>T (p.Ter214Leuext*) and a deletion of exons 1-2. A novel c.632_636del (p.Met211Argfs*) variant was found in a family involv- ing 3 generations of affected subjects. This variant is located close to the stop codon and does not lead to a nonsense-mediated RNA decay, however, clinical data indicated at potential pathogenicity of this allele. Known variant of unknown significance c.364G>A (p.Ala122Thr) was identified in a 16-years-old proband with pheo- chromocytoma. His mother was also a carrier of this variant but showed neither signs of VHL-related disorders herself, nor signifi- cant family history. Conclusion: We have not identified recurrent pathogenic variants in our small case series of Russian patients, which is in line with a rarity of founder effects for this disease. Frame-shift mutations located close to the VHL stop-codon may still render a pathogenicity. Funding: Russian Science Foundation, grant 22-45-08004 E-PS-15-038 Lung cancer and precision medicine: sample profile, morphological control, and results detected by NGS R. Silva*, R. Pinto, L. Cirnes, F. Schmitt *IPATIMUP – Institute of Molecular Pathology and Immunology of Porto University, Porto, Portugal Background & objectives: The accuracy of the molecular diagnosis is dependent on the pathological assessment of the tumour samples. This step is particularly relevant in central laboratories that receive material from several hospitals. To examine the profile of lung cancer samples and results detected byNGS. Methods: We analyse the characteristics of tumour samples and the data resulting from NGS analysis of lung cancers, studied from April to November of 2022. The cases were analysed in order to verify the per- centage of malignant nuclei (PMN), made by a pathologist (in intern- ship) and technician, and the correlation between the morphological assessment of PMN, and the allelic fraction (AF) detected. Results: From 1501 lung cancers, 66.7% (1001 cases) presented at least one alteration. The estimated average of PMN present in the samples was 36%. Samples with estimated tumour content <30% corresponded to 42.3%. The allele frequency was collected for 879 of the 1001 cases. In 70.8% of the cases, we observed an expected relation between PMN and AF of the mutated genes by NGS. No correlation was observed in 29.2%, with a low PMN compared to the AF (more than 90%). The specific detected genetic anomalies showed clinical actionability of molecular targets in 86.4% of cases. The genes more frequently mutated were KRAS (38.7%), EGFR (30.4%), MET (5.8%), BRAF (5.5%), and HER2 (3.3%). Conclusion: Our study showed that, in non-centrally collected lung cancer tissues, small samples with limited tumour cell content cor- responded to almost half of the cases. We observed a good agreement between the estimation of PMN and the AF. The discrepancies—under- estimation—can be explained by multiple hits in some of the genes tested. The morphological control with dedicated molecular pathology that evaluates the feasible material before proceeding to any molecular test ensures the accuracy of the analysis by NGS. E-PS-15-039 Ultra-fast NGS in lung cancer with HER2 mutation (ERBB2): Is the detected allele frequency the same when compared to the fast- NGS assay? R. Silva*, L. Cirnes, F. Schmitt *IPATIMUP – Institute of Molecular Pathology and Immunology of Porto University, Porto, Portugal Background & objectives: Molecular diagnosis of lung cancer is a constantly evolving field. The implementation of Ultra-fast NGS plat- form in the detection of actionable mutations is being analysed and adjusted. Our objective was to analyse the allelic fraction detected by fast and ultra-fast NGS technologies.