ECP 2023 Abstracts

S342 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 (NSCLC), several clinical practice gaps still remain. We hypothesized that we could sign-out the report of a large next-generation sequencing (NGS) panel in three working days. Methods: A prospective cohort of early and advanced NSCLC diag- nosed at Hospital 12 de Octubre were considered. At the tumour board, four patients per week were included in the ultrafast workflow. We performed a large NGS panel (Oncomine Comprehensive Assay v3, Thermo Fisher) for screening of mutations, copy number variations and fusions in 161 genes, using a fully automated workflow. Results: Comprehensive genomic profiling using NGS was performed successfully on all 44 patients in less than 3 working days. The material available for all tumours had been formalin-fixed and paraffin embed- ded. The majority of the samples analyzed were core-needle biopsies (57%). The pathological characteristics of the tumours were as follows: 36 (82%) adenocarcinomas, four (9%) NSCLC not otherwise speci- fied, two large cell neuroendrocrine carcinomas (4,5%) and two (4,5%) sarcomatoid carcinomas. Seventeen (38,6%) patients had actionable findings: 8 (18%) EGFR mutations, 3 (7%) MET exon 14 skipping mutations, 2 (4,5%) ALK fusions, 2 (4,5%) BRAF mutations, 1 (2,3%) KRAS G12C mutation, and 1 (2,3%) RET fusion. Conclusion: We have successfully implemented a fully automated ultrafast NGS workflow using a large panel with a turnaround time of three working days. Our proposal can easily be adapted to different size laboratories and clinical scenarios, but it requires very effective com- munication with the team at the clinical and molecular tumour board. Funding: This study was supported by Oncomine Clinical Research Grant Program of Thermo Fisher Scientific. We also thank Instituto de Salud Carlos III (Fondos FEDER and Plan Estatal I+D+I 2013–2016 [PI14-01176, PI17-01001] and 2021-2023 [PI22-01700]), Fundacion Mutua Madrileña (AP18051-2022) and Comunidad de Madrid iLUNG Program [B2017-BMD-3884, S2022-BMD-7437]. E-PS-21-018 Pleuropulmonary blastoma: an aggressive intrathoracic neoplasm and review of literature H. Ichrak*, R. Ayadi, B. Emna, L. Farah, S. Hamza, O. Ismail, A. Ayadi *CHU abderrahmen Mami Tunisia, Tunisia Background & objectives: Pleuropulmonary blastoma are uncommon and very aggressive tumours that account for less than 0.5% of primary lung tumours. It originates from foetal lung tissue and it is typically characterized by a biphasic pattern of an epithelial and a mesenchymal component. Methods: We report a retrospective study of 5 cases of pleuropul- monary blastoma diagnosed at our department of pathology between 2004 and 2022. Results: There were 4 male and 1 female patients, aged between 6 and 61 years, with a mean age of 42. This diagnosis was established by surgical resection (n=4) and transparietal biopsy (n=1). On gross examination, tumours were described as poorly circumscribed, whit- ish or yellowish-white mass, with necrosis or haemorrhagic changes. Microscopically, the lesion appears as a biphasic malignant tumoral proliferation, partially necrotic, made up of an entangled epithelial car- cinomatous contingent and a mesenchymal contingent of the embryonic type. The immunohistochemical study shows expression of epithelial markers and of synaptophysin by the carcinomatous contingent (n=2). Immature mesenchymal contingent is positive for vimentin and smooth muscle actin (n=5). Conclusion: Pleuropulmonary blastoma is an infrequent and aggres- sive malignancy. It is associated with a high incidence of recurrence and carries a poor prognosis. E-PS-21-019 Broncholithiasis: diagnosing a rare respiratory entity H. Ichrak*, R. Ayadi, B. Emna, L. Farah, S. Hamza, O. Ismail, A. Ayadi *CHU abderrahmen Mami Tunisia, Tunisia Background & objectives: Broncholithiasis is a rare lesion, defined as the presence of calcified materials in the tracheobronchial tree. Their clinical presentation mimics obstructive lung diseases or malignancy, leading to a delay in diagnosis. Therefore, making precise diagnosis may be challenging. Methods: We report a retrospective study of 16 cases of Broncho- lithiasis diagnosed at our department of pathology between 2004 and 2022. Results: There were 9 male and 7 female patients, aged between 15 and 72 years, with a mean of 43. A past history of pulmonary tuberculosis was found in 2 cases. Thoracic CT scan was performed in all patients and showed parenchymal calcification in six cases. The diagnosis was made on surgical resection (n = 14), transparietal biopsy (n = 1), and spontaneously expelled particles (n=1). The histological examination revealed similar morphology: calcified material filling the bronchial lumen It associates lesions suggestive of endobronchial aspergillosis (n=1), amyloid deposits (n=1), a bronchogenic cyst (n=1), bronchial dilation (n=11), and non-specific lesions (n=2). The outcome was sat- isfactory in all cases. Conclusion: The rarity of broncholithiasis and the difficulty of a patho- logical diagnosis make it difficult to study which may lead to obstruc- tive complications if unresected. This entity should be considered in the differential diagnosis of some patients with bronchial obstruction. E-PS-21-020 In-situ protein expression analysis of Seizure Protein-6 (SEZ6) A. Jungbluth*, E. Hernandez, P. Ruh, N. Choudhury, N. Rekhtman, D. Frosina, M. Baine *Memorial Sloan Kettering Cancer Center, USA Background & objectives: SEZ6 plays an important role in developing and adult nervous system; it is also found in a high percentage of small cell lung carcinomas (SCLCs). We identified suitable IHC reagents and studied SEZ6 expression in a wide variety of tumours. Methods: Only a few anti-human SEZ6 antibodies are available, three were obtained commercially. Rabbit pAb (LS-B16535; LSBio), mAb SC17.14 (Creative Biolabs) and mAb 14E5 (Abcam). Appropriate immunohistochemical protocols were developed for the use on FFPE material on Leica Bond-3 automated stainer. After specificity analysis, SEZ6 expression was analysed in panels of normal tissues and a wide variety of tumours. Results: Rabbit pAb LS-B16535 did not render staining compat- ible with the presence of SEZ6 and was not further pursued; mAbs, SC17.14 and 14E5 demonstrated staining specific for SEZ6 and were used for expression analyses. Interestingly, 14E5, a rat mAb showed a more intense and consistent immunostaining compared to murine SC17.14, a subclone of mAb SC17 employed in a therapeutic anti- SEZ6 antibody-drug conjugate (ADC). SEZ6 immunostaining was most intense and homogeneous in oligodendroglioma, medullary thyroid carcinoma, and SCLC, but was also present in pheochro- mocytoma, neuroblastoma, neuroendocrine tumours of the GIT and pancreas and ganglioneuroblastoma; NSCLCs and carcinomas of various other primary sites, melanomas and several haematological neoplasms were all negative. Conclusion: SEZ6 is best detected in IHC using mAb 14E5, ren- dering intense and consistent immunostaining without any back- ground reactivity. MAb SC17.14, subclone of therapeutically employed mAb SC17, displayed less optimal staining. Besides SCLCs, SEZ6 was present in all tested neuroendocrine and neu- rological tumours albeit displaying variable homogeneity. SEZ6 is not expressed in any other tumours or tumour entity. Besides SCLC, SEZ6 appears to be a potential therapeutic target for most tumours of neural/neuroendocrine lineage and is best detected by mAb 14E5.