ECP 2023 Abstracts

S349 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 male gender, higher pT, and pN categories, and adjuvant chemotherapy. Lower elastin was associated with tobacco consumers, SqCC and LCC histology, and early disease. Col I correlated positively with the pT category; Col III, CS, and E-cadherin were both associated with age. In multivariate analysis, high SPARC and relapse were found to be a prognostic factor for decreased progression-free survival (P=0.03) when controlled for male gender, SqCC histology, tumour size, and Col III. Conclusion: Because up-regulation is frequently observed in the stro- mal and epithelial tumour compartment, EMT-ECM indicator proteins may be integrated into progression models of NSCLC, eventually allow- ing the selection of patients who can benefit from targeted therapies. E-PS-21-043 Endobronchial solitary fibrous tumour: a perfect mimic of carcinoid F. Ramalhosa*, F. Pezzuto, F. Francesco, G. Canu, E. Faccioli, C. Giraudo, F. Calabrese *Centro Hospitalar e Universitário de Coimbra, Portugal Background & objectives: Solitary fibrous tumours (SFTs) are rare mesenchymal neoplasms (less than 2% of all soft tissue tumour) com- monly arising in the thoracic cavity. However, they may occur at any site, including the lung parenchyma, pericardium, and, rarely, the bronchus. Methods: A 49-year-old woman presented to the pulmonary unit with progressive chronic cough. She was a non-smoker with history of allergy to plants, fruits and drugs. Due to progressive obstructive dysfunction an explorative bronchoscopy was performed revealing an intrabronchial mass of the left superior bronchi. Somatostatin Receptor- Based PET/CT showed high affinity to somatostatin receptors rising the main diagnosis of carcinoid tumour. Results: The patient underwent pulmonary segmentectomy and an intramucosal well circumscribed polypoid lesion of 19 mm was detected. Pathological examination revealed a low-grade mesenchymal spindle cell neoplasm arranged in sheets and storiform pattern without necrosis. The tumour cells had mild atypia with low mitotic index (1 mitosis/mm2). The lymph nodes and margins were negative. The immunohistochemical analysis was positive for STAT6, and negative for S-100, MDM2, cytokeratin, chromogranin A,and synaptophysin. The proliferation index (Ki-67) was 5%. Based on the histopathological and immunohistochemical findings the diagnosis of a bronchial SFT was made. The patient became asymptomatic after lesion’s excision, and during the 6-month follow-up there were no recurrences. Conclusion: Endobronchial SFT are unusual. To the best of our knowl- edge only five cases have been reported in the literature. Carcinoid is the main mimicker sharing clinical and radiological characteristics. Considering the location and the features at imaging mucoepidermoid carcinoma, endobronchial pleomorphic adenoma, hamartoma or leio- myoma and, last but not least, metastases should be considered among the differential diagnoses. This report highlights the importance of careful histological and immunohistochemical evaluation for an accu- rate diagnosis and appropriate risk stratification of this lesion. E-PS-21-044 SMARCA4 deficiency in poorly differentiated/ undifferentiated non-small cell lung carcinoma G. Raskin*, A. Fedorova, M. Mukhina, R. Orlova, M. Kleshev *Dr. Berezin Medical Insitute, Russia Background & objectives: SMARCA4-deficient lung tumours are highly aggressive malignancies without mutations in EGFR, ROS1, or ALK genes. The aim of the study was to evaluate the frequency of SMARCA4-deficient tumours in patients with poorly differentiated and/or undifferentiated non-small cell lung carcinomas (NSCLCs). Methods: 133 cases of poorly differentiated NSCLCs were studied immu- nohistochemically using the anti-BRG1 (SMARCA4) and anti-SMARCA2/ BRM (Abcam) antibodies. The expression of TTF1 (Leica), p63 (Agi- lent) was also investigated. Specimens considered SMARCA4 and/or SMARCA2-deficient if negative reaction observed in tumour cells, while stromal cells showed positive nuclear staining. EGFR, BRAF, ROS and ALK mutations were analysed retrospectively in such cases. Results: 26 cases (19,5%) of NSCLCs were identified as SMARCA4- deficient. There were 21 men and 5 women with average age 61.3±1.9. In 20 SMARCA4-deficient tumours, a negative TTF1 or p63 reaction was detected. In addition, 14 of 20 tumours showed a combined loss of both markers. SMARCA2 expression was studied in 24 SMARCA4-deficient tumours. Complete loss of both markers was found in 5 cases (20,8%), and a focal attenuation of SMARCA2 expression was noted in 3 cases (12,3%). The rest 16 tumours were SMARCA2 -positive. EGFR, BRAF, ROS and ALK mutations were not detected in any of the cases. Conclusion: According to our investigation SMARCA4-deficient tumours occurred in 20% of poorly differentiated NSCLCs. Predomi- nantly these tumours were TTF1/p63 negative and often demonstrated loss of SMARCA2 expression (33%). As SMARCA4-deficient tumours respond poorly to standard therapy in comparison with other poorly differentiated and/or undifferentiated lung tumours, further study with an assessment of prognostic and predictive value of these markers is recommended. E-PS-21-045 The combination of PDL-1 expression and TIL levels as predictors of response to immunotherapy in non-small cell lung carcinoma R. Rendón García*, J.d.B. Machuca Aguado, M.L. Bernal Sanchez, F.J. Rubio Garrido, J.J. Rios Martin, M.A. Idoate Gastearena *Virgen Macarena University Hospital, Seville, Spain Background & objectives: Immunotherapy has been a revolution in the treatment of non-small cell lung carcinoma (NSCLC). However, its high cost and limited availability highlights the needing of prognostic and predictors biomarkers, being the tumour infiltrating lymphocytes (TILs) a possibility. Methods: This is a retrospective observational clinicopathological study of a series of 29 patients with NCLSC treated with immunotherapy. They had a median follow up to 40 months. The level of PDL1 expres- sion was determined immunohistochemically. The number of stromal and intraepithelial CD8+ TILs were assessed by two observers and cut-off points were established according to the Donnen classification. Results: The relationship between PDL-1 and overall survival was sta- tistically significant (r= 0,341; p= 0.03).When patients were divided in 4 subgroups according to PDL-1, high (>50%) or low (<50%) expres- sion, and intraepithelial TILs, high (>25%) or low (<25%) level, those in the high-PDL-1 and high-TILs-CD8+ subgroup were associated with the highest overall survival (p=0.047). Conclusion: We consider that the quantification of PDL-1 and CD8+ TILs could be adequate biomarkers to perform a clinical approach to patients. These biomarkers can be predictors of immunotherapy response and prognostic of survival, being of better prognosis those patients with elevated levels of both parameters. E-PS-21-046 A comparison of pulmonary placental transmogrification with immature placenta L. Rothenbächer*, J. Knolle, M. Krüger, W. Schütte, E. Gradhand *Krankenhaus Martha Maria Halle Dölau, Institut für Pathologie, Germany Background & objectives: Pulmonary placental transmogrification (PPT) represents an extremely rare benign lesion of the lung and histo- morphologically, it resembles immature placental villi. We compare