ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 and lung-to-lung metastasis. ERBB2 mutated cases with exon 20 insertions showed heterogeneous immunoreactivity with mostly weak basal cytoplasmic and membranous patterns (0, 35%; 1+, 40%; 2+, 25%). Two out of five point mutations displayed mod- erate membranous staining (2+, 100%). Among the 19 ERBB2- amplified cases with CN ≥ 7, 14 cases exhibited a strong complete circumferential pattern (3+). The remaining 5 cases displayed mod- erate basolateral staining (2+) and were accompanied by actionable EGFR, KRAS, and ERBB2 exon 20 mutations. Conclusion: ERBB2 amplification shows a high correlation with protein overexpression, being predicted by IHC. ERBB2 ampli- fication can be accompanied by other actionable mutations with discordant ERBB2 protein expression. On the other hand, ERBB2 mutations usually occur in a mutually exclusive manner with other driver mutations. They show heterogenous ERBB2 expression with negative to moderate cytoplasmic and membranous staining. PS-16-010 A single-institution experience of pulmonary sarcomatoid carcinoma O. Mnif*, R. Ayadi, E. Braham, M. Mlika, A. Rais, O. Ismail, A. Ayadi, F. El Mezni *Abderrahmen Mami Hospital, Tunisia Background & objectives: Pulmonary sarcomatoid carcinoma (PSC) is an uncommon tumours, accounting 0.1 to 0,4 % of all lung cancers. It is a highly invasive tumour. The WHO distinguish 3 subgroups: pleomorphic carcinoma, carcinosarcoma and pulmonary blastoma. The aim: discuss clinicopathological characteristics and immunohis- tochemical features of these tumours. Methods: This retrospective study included all patients with a pathologically confirmed diagnosis of PSC treated at our depart- ment of pathology between 2005 and 2021. Results: There were 78 male and 11 female patients, aged between 6 and 82 years with a mean of 61. The diagnostic was made on surgical resection (n=56), on transparietal biopsy (n=27) and on a resection of metastatic location (n=10). An intraoperative frozen section was performed (n=36) showed inflammatory lesion (n=5) and non small cell carcinoma (n=31). The histological examination revealed pleomorphic carcinoma (n=66), Carcinosarcoma (n=9), pulmonary blastoma (n=5) and unclassified tumour (n=9). Immunohistochemically, the tumour cells were positive for vimentin (n=50), TTF-1 (n=19), EMA (n=14), cytokeratins (n=41). However, they were negative for muscle actin, PS100, actin, and calretinin. Conclusion: The rarity PSC and the difficulty of pathological diagnosis make it a difficult malignancy to study. It pose a sig- nificant challenge due to their rare occurrence, heterogeneous histology, and unclear histogenesis. PS-16-011 Complexity of screening methods for gene fusions in molecu- lar pathology labs L. Carvalho*, M.R. Silva, A. Alarcão, A. Ladeirinha, T. Ferreira, A. Rodrigues, C. Vilasboas, V. Sousa *1 Anatomical Pathology Department, Hospitais da Universi- dade de Coimbra, Centro Hospitalar e Universitário de Coimbra, Portugal; 2 Institute of Anatomical and Molecular Pathology, Faculty of Medicine of the University of Coimbra, Portugal Background & objectives: Gene fusion in NSCLC involving ALK, ROS1, and RET are demanded for benefit from targeted tyrosine kinase inhibitors. Detection and identification of fusion events might be com- plex even with specific screening methods. Methods: Fluorescence in situ hybridization (FISH) has cur- rently been used as a sensitive method for screening ALK, ROS1 and RET fusions. RT-PCR specificity is recognized for target specific primers, of known fusions and exon skipping events. DNA/RNA NGS methods have evolved to detect fusions without previous information of gene partners and for diverse genetic events. Results: Breakapart FISH with 5´/3´probes for screening ALK, ROS1 and RET rearrangements lack information regarding the gene partner fusion. Aberrant FISH patterns and false-positive results may be due to a possible non-functional oncogenic fusion. Immunohistochemistry (IHC) is accurate for protein detection for ALK, but not for ROS1 and RET, due to poor specificity in the lung. RT-PCR as less sensitive method, only detects known gene partner fusions and unknown or new partners will be missed. DNA-NGS reads at specific base position breakpoints and can identify fusion variants, while RNA-NGS identifies known and unknown fusions at the transcript level. Conclusion: FISH is a sensitive method for detecting breakapart rearrangements but also unspecific due to the lack of information regarding functional fusions. A validated method must be used to confirm aberrant cases. DNA-NGS has revealed many uncom- mon ALK, ROS1 and RET fusions, events at genomic level not corresponding to fusion transcripts at the RNA level. Molecular Pathology Labs validated RNA-NGS level as necessary to detect rare fusion events, to determine which patients will benefit from actual targeted therapy. PS-16-012 A multicentric Portuguese study for the assessment of PD-L1 score in NSCLC using 22C3 and SP263 clones on Ventana’s platform: a stepping stone for the IVDR legislation landscape? V. Sousa*, A. Luis, A. Ribeiro, C. Souto de Moura, I. Rolim, A.L. Cunha, C. Quintana, C. Eloy, E. Pinto, F. Cunha, J. Correia-Pinto, L. Carvalho, J. Vizcaino, C. Coelho, F. Ferreira Carlos, P. Borralho *Institute of Anatomical and Molecular Pathology, Faculty of Medicine of the University of Coimbra; CIMAGO – Research Center for Environ- ment, Genetics and Oncobiology, Faculty of Medicine, University of Coimbra; University Hospital Anatomical Pathology Coimbra, Portugal Background & objectives: Anti-PD-L1 immunotherapy is used for NSCLC treatment. Different clones, platforms and scoring methods can be used to evaluate PD-L1 expression as a predictive biomarker. We compared the performance of 22C3(LDT) and SP263(IVDR) assays, in a prospective non-interventional multicentric Portuguese study. Methods: 391 lung cancers; 264 adenocarcinomas (ADC; 67.5%); 98 squamous cell carcinomas (SqCC; 25.1%) and 29 other subtypes NSCLC (7.4%) were collected from 14 Portuguese centres. 22C3 LDT and SP263 IVDR assays were performed on Ventana plat- form. PD-L1 expression was determined by TPS(Tumour Propor- tion Score). Cohen’s Kappa coefficients were calculated. Nominal variables were analysed using the chi-square test (statistical sig- nificance p<0.05). Results: No statistically significant differences were found between 22C3 and SP263 clones when considering the type of sample [biopsy (n=258, 66%) vs surgical specimen (n=133; 34%)] and the histological subtype. Biopsies demonstrated higher 22C3 scores (TPS>=1 or >=50%) than surgical specimens (p=0.013; p=0.023) and also higher SP263 scores (TPS>=1 or >=50%) (p=0.014; p=0.009). The number of samples 22C3 PD-L1 <1% was significantly higher in ADC when compared to SqCC (p=0.032). Excellent Kappa agreement / concordance was observed for PD-L1 S152