ECP 2023 Abstracts

S348 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 lobe. Both MSCT and intraoperative consultation pointed out the D/D between NET and other benign lesion, so lobectomy was decided. Results: The tumour was well circumscribed, nonencapsulated, with a cut surface tan-yellow to grey. Histopathological sections revealed a solid and a papillary pattern. The neoplastic cells were medium sized, with oval nuclei and distinct nucleoli, with abundant eosinophilic cytoplasm. The mitotic activity was low (Ki67 5%) and there was absence of necrosis. The intermediate stroma was sclerotic with haemorrhage and chronic inflammation. The pleura were free of neoplastic invasion. Both the neoplastic cells were immunohistochemically positive to TTF-1, CD56, CK18, Napsin A, while the papillary component was CK7(+) and ER(+) and the solid component was ER/PR(+). All lymph nodes were disease- free and the surround parenchyma showed areas of emphysema and atelectasis. Conclusion: Sclerosing pneumocytoma can present as solid tumour with biphasic pattern and is challenging to distinguish from adeno- carcinoma or carcinoid tumour on frozen sections. It was usually seen in the fifth-decade female, which was possibly attributed to the presence of progesterone receptors. Possible malignant characteris- tics with lymph node metastasis or local recurrence have been docu- mented. Sublobectomy, segmentectomy and wedge resection, tended to be preferred for peripheral small-sized tumour, while lobectomy could prevent potential metastasis and recurrence which would worse long-term prognosis. E-PS-21-040 Endobronchial lipoma: an incidental finding during bronchoscopy E. Psychogiou*, P. Tziakou, P. Megas, M. Miliou, K. Papadopoulou, A. Konstantinidou, E. Papadopoulou, D. Riga, C. Glava, I. Vamvakaris *General Hospital of Athens Sotiria, Greece Background & objectives: Endobronchial lipoma is a rare benign neoplasm accounting for only 0.1%–0.4% of all bronchial tumours and is composed exclusively of mature fat. It is difficult to differenti- ate benign from their malignant counterparts, as their symptoms and complications are alike. Methods: A 66-year-old man was admitted to our hospital complain- ing of irritant cough. Chest radiography showed atelectasis of the right lung and MSCT scan demonstrated a mass on right upper lobe. During fibreoptic bronchoscopy, a well-circumscribed polypoid mass, measur- ing 0,4X0,2 cm, protruding into trachea was incidentally found and was successfully excised. Results: The biopsy specimen was a well circumscribed tumour with a uniform glistening yellow surface. Histopathological sec- tions revealed bronchial tissue covered by benign epithelium, benign seromucinous glands and mature adipose tissue. No malignant cells were seen. There was absence of cartilage, myxoid matrix, entrapped bronchial epithelium, or other mesenchymal components. The presence of fat attenuation narrows down the differential diag- nosis to the following: pure endobronchial lipoma, which demon- strates homogeneous fat attenuation; fibrolipomatous tumour, which contains soft tissue attenuation with islands of fat; and hamartoma, which has fat density alternating with calcific foci and other mes- enchymal components. The tumour was pathologically confirmed as endobronchial lipoma. Conclusion: This case suggests that an endobronchial lipoma can pre- sent as incidental finding. Patients are middle aged with a strong male predominance. Clinically, these patients most often present with cough and symptoms of chest infection. CT examination is highly specific and sensitive for the detection of fat. Endoscopic resection is usually the first line of treatment, as it is both diagnostic and curative. Recurrence of endobronchial lipoma is exceedingly rare after complete surgical resection. E-PS-21-041 Semi-automated microscopic evaluation of mesothelin and immune landscapepredicts survival after surgical resection of malignant mesothelioma A. Qualiotto*, C. Machado Baldavira, M. Balancin, A. Ab’Saber, T. Takagaki, V.L. Capelozzi *Laboratory of Genomic and Histomorphometry, Department of Pathology, University of Sao Paulo Medical School, Brazil Background & objectives: Anti-mesothelin and anti-PD-L1 emerged as promising drugs to inhibiting the invasion of malignant mesothelioma (MM) and restoring the immune landscape. Thus, we sought to study the relationships between mesothelin and the immune landscape in MM. Methods: We examined mesothelin, immune cells (CD4, CD8, CD68, CD20), and PD-L1 markers in tumour tissues from 82 patients with MM. All our patients were stage III/IV, and 50.6% of patients had been exposed to asbestos. We used immunohistochemistry and quantitative digital analysis (QuPath software) to evaluate the amount of tumour staining for mesothelin, immune cells, and PD-L1. Results: Our results showed that high mesothelin expression was associated with male (P=0,013) and sarcomatoid histotype (P<0.01). High CD4 expression was associated with not asbestos exposure and alive patients (P<0.01, for both). High CD8 expression was correlated with epithelioids histotype, while high PD-L1 expression was associ- ated with women (P=0.03, for both). When combined the expressions CD4 and CD8, the increased expression this combination was associ- ated with no asbestos exposure and alive patients (P<0.01, for both). Multivariate Cox model analysis, controlled for asbestos, histological type, and PD-L1 expression, demonstrated that quantitative staining of the tumour for mesothelin and CD4 added prognostic information (P=0.001 and P=0.016, respectively). Conclusion: Tumour staining for mesothelin, CD4, and PD-L1 in resected MM of the pleura are strongly related to survival. Patients with staining for mesothelin >23.96%, and PD-L1 >0.58% in their tumours, after 40 months of follow-up comprise a subset with a high hazard of dying of MM, while patients with CD4 >0.7% in their tumour presented better survival. These findings suggest that those markers may be an appropriate target for prospective studies of adjuvant immu- nobiological agents combined with immune checkpoint proteins. E-PS-21-042 Increased epithelial-mesenchymal transition transdifferentiation proteins increasesextracellular matrix proteins in invasive non- small cell lung carcinomas C. Machado Baldavira, A. Qualiotto*, M.L. Fernezlian, S. Fern- ezlian, A.P. Pereira Velosa, W. Rosolia Teodoro, A. Ab’Saber, T. Takagaki, V.L. Capelozzi *Laboratory of Genomic and Histomorphometry, Department of Pathology, University of Sao Paulo Medical School, Brazil Background & objectives: In NSCLC, invasion is defined as tumoral infiltration into stroma, be enhanced by the epithelial-mesenchymal transition (EMT) process. We hypothesize that the density of extracel- lular matrix (ECM) proteins and expression levels of EMT-proteins may correlate with clinicopathologic variables and outcomes. Methods: We analysed the protein expression of the EMT indicators E-cadherin, B-catenin, and SPARC as well as of the putative ECM indicators fibrillin, elastin, heparan sulfate (HS), chondroitin sulfate (CS), collagen types (Col) I, III, IV, and V in both intratumoral stroma and carcinoma cells in a cohort of NSCLC (n=81) by immunohisto- chemistry quantification by digital analysis (QuPath software). Results: We observed a significant moderated correlation between fibrillin vs SPARC, elastin vs SC, HS vs SPARC, E-cadherin vs β-catenin, and E-cadherin vs Col III. Lower fibrillin was associated with