ECP 2023 Abstracts

S350 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 the histological findings and iimmunohistochemical expression of the PPT with immature placenta. Methods: Histological H+E- and immunohistologically stained sec- tions of a pulmonary placental transmogrification of a 40 year old for- mer smoker and an immature placenta of the 12th week of pregnancy of a 39 year old woman are compared. Results: Histologically, the PPT show a cavernous placental-ilike neoplasia without atypia or atypical mitoses. Pre-existing pneumo- cytes express TTF-1. The epithelium expresses AE1/AE3. Vascular structures express CD31 and CD34. Lymphangioma-like structures express D2-40. Scattered single CD117 positive mast cells are seen. The stroma cells are moderately CD10-positive but positive for Actin and with negativity for Desmin. Ki67 marks 1% oft he lesional cells. Isolated Progesterone and PAX8 positive cells with negativity for Oes- trogen are seen. Immunohistochemistry of immature placenta shows a similar result. Though, TTF-1, Progesterone, PAX 8 are not expressed. However, Desmin, BetaHCG and PLAP are positive in placental tissue, which were not expressed in PPT. Conclusion: Pulmonary placental transmogrification and immature placenta are very similar histomorphologically. Even though, the immature placenta of the 12th week of gestation shows villi with a double-row trophoblast epithelium; in the PPT, the epithelium is deli- cately single-rowed and the villi-like structures are more rounded. Immunohistochemically, they show some similar expression pattern. Nevertheless, there significant differences in immunohistochemical expression with BetaHCG and PLAP negativity in PPT. E-PS-21-047 Next generation sequencing in non-small cell lung carcinoma: two- year institution experience S. Sáez-Álvarez*, M.G. Rodríguez-Guevara, C. Diez-Tascón, S. Medina-Valdivieso, C. Martínez-Martínez, B.I. Tavara-Silva, S. Marín- Asencio, L. López-López *Complejo Asistencial Universitario de León, Spain Background & objectives: Multigene analysis by Next Generation Sequencing is recommended by ESMO in patients presenting with advanced non-squamous Non-Small Cell Lung Carcinoma (NSCLC). The present work aims to describe the NGS results obtained in our institution for NSCLC in a two-year period. Methods: Tumour samples obtained from consecutive patients diag- nosed during 2021 and 2022 underwent targeted NGS analysis using a 52 genes panel (Oncomine Focus Assay, ThermoFisher), including DNA variants, copy number variants (CNV) and gene fusions. Data was processed using Microsoft Excel and IBM SPSS. Results: 297 samples of NSCLC from 287 patients underwent NGS during this period. Most patients were males with an average age of 68.3 years. Active/former smokers accounted for 63%. Most samples were biopsies (63.3%), the rest corresponding to cytology and Fine- Needle Aspiration. Molecular alterations were found in up to 72% patients, with EGFR and KRAS being the most frequently altered genes. EGFR mutations were identified in 14.5% tumours (45.7% deletion exon19; 28.6% p.L858R). KRAS mutations accounted for 35% (41,2% p.G12C). Translocations showed lower frequency (3% ALK; 1.3% ROS1; 1.7% RET). Other single nucleotide variants (SNV) were also present (5.1% BRAF; 6.7% PIK3CA). MET exon14 skipping was identified in 5 tumours (2.7%). Conclusion: NGS is a sensitive and specific technique to identify molecular alterations affecting predictive biomarkers of NSCLC. Biopsy and cytology samples are both eligible for NGS. A large per- centage of NSCLC harbour molecular alterations with clinical and/or therapeutic value. Alterations in biomarkers found this work are similar to those described in other studies performed in our country. E-PS-21-048 A peculiar case of endometrioid type adenocarcinoma of lung C. Stamou*, K. Iliadis, M. Sotiropoulou *Department of Pathology, Hygeia Hospital, Athens, Greece Background & objectives: Adenocarcinoma with endometrioid type morphology of lung is rare and is usually seen in the context of pri- mary foetal adenocarcinoma or metastatic disease from gynaecological adenocarcinoma. We present a case of a 47y.o. woman without history of myllerian endometrioid adenocarcinoma. Methods: A right lower lobectomy specimen was received, in multiple sectioning of which two compact and whitish nodules of 2.6 cm and 1.4 cm in maximum diameter were found. Results: The histological examination of both nodules revealed well demarcated neoplastic lesions composed of glandular either tubular formations lined by pseudostratified epithelium of cylindrical cells with eosinophilic cytoplasm, ovoid to elongated nuclei, coarse chromatin and incospicuous nucleoli. There were also focal back-to-back and cri- briform configurations, numerous morules and rare squamous metapla- sia. Moreover, tiny nodules of immature chondroid tissue were present. Upon immunohistochemical control, neoplastic cells were positive for Pax8, ER, PgR, CK7 and AE1/AE3, with membranous expression of β-catenin stain and wild-type staining pattern of p53. Further immu- nohistochemical control with TTF1, AFP and Vimentin was negative, while morules were positive for CD10. Conclusion: A diagnosis of low grade endometrioid type adenocar- cinoma was made, probably of myllerian origin. We also stated the probabilities of primary lung endometrioid adenocarcinoma arising in lung endometriosis and of low grade foetal adenocarcinoma/pulmonary blastoma. Radiological examination revealed no mass in uterus and ovaries, however a total hysterectomy with bilateral salpingo-oopherec- tomy was decised, after multiple sectioning and examining of which no neoplastic areas were detected. Next generation sequencing of multiple genes from lung nodules revealed mutations in CTNNB1, PTEN and PIK3CA genes. E-PS-21-049 Lung Epithelioid Hemangioendothelioma (EHE) with YAP-1-TFE3 fusion: diagnostic approach in endobronchial biopsy N. Stavrinou*, F. Dolkiras, E. Spiteri, E. Athanasiou, E. Papagianni *Department of Pathology, Evaggelismos General Hospital Athens, Greece Background & objectives: Epithelioid haemangioendothelioma of the thorax is a malignant vascular neoplasm, usually intraparenchymal, less often pleural, rarely mediastinal. It affects mostly young people. Patients often present with metastatic disease; therefore its prognosis seems to be worse than the soft tissue counterpart. Methods: A 37-year-old man, smoker, presented with haemoptysis due to a large mass in the hilum of the right lung. An endobronchial biopsy was performed and sent for pathologic evaluation. The tissue sample was fixed in 10% neutral buffered formalin, processed and embedded in paraffin. Results: Microscopically, bronchial mucosa was infiltrated by an epi- thelioid malignant neoplasm consisting of relatively uniform tumour cells of plasmacytoid or rhabdoid morphology, with moderate nuclear atypia, mostly arranged in a solid pattern around vessels or form- ing rudimentary vascular spaces. Mitotic activity was estimated at 6/50HPF. Spindle cell morphology and necrosis were absent. Immu- nohistochemically, tumour cells were positive for vascular markers (CD31, D2-40, FVIII, ERG, Fli-1) as well as TFE3, Vimentin, CD56, and CD163. Cytokeratins, neuroendocrine, melanocytic, and lympho- cytic markers were negative. In situ hybridization for YAP1-TFE3 fusion was also performed. Ki67 was estimated at 35%.