ECP 2023 Abstracts

S22 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 No recurrences were reported during follow-up. One AIS patient died 22 months after surgery, while another developed a lung adenocarci- noma after 65 months (LCSS=92,9% for AIS and MIA cases together). Conclusion: Our casuistic aligns with most publications that report a near 100% rate of RFS, even with longer follow-ups. This result highlights the importance of distinguishing AIS and MIA from other pulmonary adenocarcinoma stages. Moreover, we report the occurrence of one metachronous lung car- cinoma during follow-up. This finding is also in line with the recent recognition of high rates of secondary lung tumours in patients with previous AIS and MIA, supporting long-term follow-ups after surgery. OFP-05-012 A comparative analysis of proficiency testing for the biomarkers ALK, ROS1, EGFR, KRAS and BRAF in non-small cell lung can- cer (NSCLC) using the IHC,ISH and MolPath methodologies A. Ryška, S. Merkelbach-Bruse*, D. Jonigk, E. Schuuring, I. Kern, D. Dawodu, K. Ilm, K. Jöhrens *University Hospital Cologne, Germany Background & objectives: NSCLC accounts for about 85% of all lung cancer cases. Accurate and reliable identification of several biomark- ers are critical for guiding the treatment decisions. We present the outcomes of the proficiency-test programs that involved participation of over 100 European laboratories. Methods: QuIP GmbH provided 5 cases of 1 FFPE section to the par- ticipating laboratories for the IHC&ISH (ALK&ROS1) testing and 5 cases of 2 FFPE sections for the molecular pathology testing (EGFR, KRAS and BRAF).The anonymized results and reports were reviewed by experts and sent to participants to help improve their diagnostic performance and facilitate benchmarking of their results. Results: The number of participation and the error rate in % for each sub-scheme of the proficiency tests are: 60 and 20 % for ALK (IHC), 42 and 12 % for ALK (ISH), 46 and 37 % for ROS1 (IHC), 41 and 7 % for ROS1 (ISH), 79 and 9 % for EGFR, 48 and 2 % for KRAS and 51 and 2 % for BRAF. A broad range of methodologies were used by participants making it challenging to correlate specific methodologies with the pass / fail rates. Conclusion: The number of participation indicates a growing rec- ognition of the importance of proficiency testing. The unsuccessful participants commonly faced issues related to the use of inadequate controls, staining inconsistencies, incorrect interpretation of results, and inaccurate labelling and documentation of results. Despite the promising results of the proficiency tests, these issues could have sig- nificant consequences for patient care highlighting the importance of regular proficiency testing and continuous monitoring to ensure high standards of quality and accuracy. OFP-05-013 ROS1 SP384 clone and ROS1 FISH concordance in non-small cell lung cancer: a clue for oncogenic driver mutations C.A. Gomez Gonzalez*, B. Yaman, G. Serin, A. Veral, D. Nart *Department of Pathology, Ege University Faculty of Medicine, Turkey Background & objectives: In Turkey, lung cancer is the most com- mon cancer type in men and women. For molecular diagnosis, local guidelines have been developed. We present the status of ROS1 gene mutation by comparing immunohistochemistry (IHC) and FISH in a single centre in Turkey. Methods: 201 biopsies performed in Ege University Hospital and con- sultation material referred for molecular studies during the period of 2019 and 2022 were evaluated. Tissue and cytology specimens with the diagnosis of NSCLC were included. Demographic information, histologic type, ROS1 SP384 immunohistochemistry staining pattern (H-Score), and at least reflex molecular testing of three genes (EGFR, ALK, and ROS1) were recorded. Results: 34 cases (16,9%) had positive results for ROS1 IHC. ROS1 FISH was positive in 7 cases from the cohort (3,48%);5 cases with positive ROS1 IHC staining (5/34; 14,7%) and 2 cases without staining (2/167; 1,19%). The average H-score for FISH-positive cases was 152. Additionally, ROS1 IHC was positive in cases with ALK, EGFR, and KRAS mutation; one case had synchronous EGFR and ROS1 muta- tion. ROS1 SP328 clone sensitivity and specificity were 71,43%(95%CI 29,04 to 96,33%) and 85,05%(95%CI 79,24% to 89,75%) respectively, NPV of 98.80%(95%CI: 96.23% to 99.63%); adjusting H-scores above or equal to 150, sensitivity and specificity values were 42,86%(95%CI 9,9% to 81,59%) and 97,42%(95%CI 94,09% to 99,16%) respectively, NPV 97,93%(95%CI: 94,78% to 97,93%). Conclusion: ROS1 IHC assessment in lung cancer as a screening tool is helpful to suspect molecular alterations in positive cases, revealing ROS1 rearrangement and/or other oncogenic driver mutations. Evaluation with the FISH technique should be performed. In discordant cases with no molecular correlation of ROS1, ALK, KRAS, or EGFR; NGS or RT-PCR for ROS1 can be run to exclude rare mutations or undetected fusion partners with FISH. ROS-1 rearrangement can have co-mutations with EGFR, KRAS, and ALK setting a challenge for medical treatment. OFP-05-014 Ki-67 and PHH3 score in grading mesothelioma: comparison between cytological and surgical specimens D. Vurallı Bakkaloğlu*, Y. Ozluk *Istanbul Faculty of Medicine, Pathology Department, Turkey Background & objectives: Grading mesothelioma can be challeng- ing especially in cytological and limited tissue biopsies. We aimed to investigate the role of Kİ-67 and PHH3 scores in distinguishing poor outcome patients by evaluating cytological and surgical specimens. Methods: Twenty-one pleural mesothelioma cases that has been diag- nosed both by cytology and surgical specimens were included in the study. Descriptive data, nuclear atypia, mitosis count, necrosis, nuclear grade, tumour grade, histologic subtype, Ki-67 and PHH3 score were evaluated. Material adequacy for evaluation was noted as high power fields for cytol- ogy. Comparison tests and survival analysis were performed. Results: Seventy-six percent of the patients were male. Mean age was 57.52±10.31 years. Median survival time was 20.00±4.94 months. Histo- logic subtypes were as follows: 66.7% epithelioid, 23.8% biphasic and 9.5% sarcomatoid. High grade mesothelioma was diagnosed only by resection materials, but not by cytology. PHH3 scores (0.62±0.81, 2.10±1.61), mito- sis count (13.76±15.36, 27.05±24.05) and Ki-67 scores (19.57±18.89, 35.81±24.87) were found higher in surgical specimens (p<0.002). High mitotic count (≥2) and Ki-67 score of ≥30%were found as poor prognostic factors in both cytological and surgical materials (p<0.05). Conclusion: High mitosis count (≥2) and ≥30% Ki-67 score can be a useful tool to predict prognosis both in cytology and surgical materials. Reporting these findings may help the clinician to manage the poor outcome patients. OFP-06 | Joint Oral Free Paper Session Endocrine Pathology / Head and Neck Pathology OFP-06-001 Papillary microcarcinoma – does size still matter? G. Fontinha*, M.J. Martins *Centro Hospitalar e Universitário de Coimbra, Portugal Background & objectives: Papillary microcarcinoma of the thyroid is a papillary carcinoma with ≤10 mm. Although it carries an excellent prognosis it may metastasize, and this behaviour is difficult to predict.