ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 by conservative and complete surgical excision. Recurrences are infrequent in classic OF but more common in Juvenile ossifying fibroma. Therefore, a complete excision with long term supervision is needed. PS-02-011 Verification and validation of the anti-PD-L1 antibody, clone 22C3 on a laboratory developed test S. Brennan*, J. O’Neill, S. Kennedy *St. Vincent’s University Hospital, Dublin, Ireland Background & objectives: PD-L1 IHC 22C3 pharmDx assay kit processed via the Dako Autostainer Link-48 platform is the licensed immunohistochemical assay and companion diagnostic test(CDT) for the assessment and thus administration of Pembroli- zumab. However, laboratories may not have access to this specified CDT. Methods: 47 whole tumour slides off head and neck squamous cell carcinomas were stained with the PD-L1 IHC 22C3 pharmDx assay kit processed via the Dako Autostainer Link 48 (CDT) and the Dako Omnis platform, referred to as a laboratory developed test (LDT). A combined positive score (CPS) were provided by 2 pathologists, with discordant cases provided with an agreed score. Results: PD-L1 IHC 22C3 pharmDx assay kit processed via CDT and LDT showed identical staining in terms of intensity and pattern of staining. On review of concordance between the CDT and LDT, implementing a CPS cut-off of ≥ 1 showed the following: overall percentage agreement (OPA) 94%; positive percentage agreement (PPA) 100%; negative percentage agreement (NPA) 88%. A CPS cut-off of ≥ 20 showed the following: OPA 96%; PPA 95%; NPA 100%. With a CPS cut-off of ≥ 1, the intra-examiner concordance between the platforms was 89%, and the inter-examiner concord- ance between examiners on each platform was 92%(CDT) and 85%(LDT). Conclusion: Firstly, the high level of concordance between scoring Pathologists illustrates with adequate training there is a reduction in the variable of scoring interpretation by examiners, which may have a therapeutic implication. Secondly, we open for discussion the deconstruction of the current practice of a compulsory CDT for a particular PD-L1 immunohistochemical assay in head and neck cancers. The implementation of LDTs as an alternative to the CDT are a novel and readily available method to surmount limitations posed. PS-02-012 The accuracy of head and neck core needle biopsies and fine needle aspirates at a large teaching hospital P. Hankinson*, R. Gorania, A. Khurram *The University of Sheffield, United Kingdom Background & objectives: Fine needle aspirate and core needle biopsies are common techniques for diagnosis of head and neck diseases. Diagnosis can be challenging due to limited tissue for examination. Here we record the accuracy of these techniques at Sheffield Teaching Hospitals. Methods: We accessed records of patients receiving core needle biopsy (CNB) or fine needle aspirate (FNA) at a head and neck site from 2015 to 2020. Cases without definitive diagnosis on subsequent excision were excluded. Both specific diagnosis and benign/malignant category was compared between CNB/FNA and the excision specimen. Accuracy of FNA and CNB was compared with a Fischer’s exact test. Results: A total of 79 cases were identified in which the CNB/ FNA diagnosis could be compared with a definitive diagnosis made on an excision specimen. Of these, 63 cases were CNB and 16 were FNA. CNB showed 95% agreement between the benign and malignant category and 87% in specific diagnosis. FNA showed 94% agreement between the benign and malignant category and 69% in specific diagnosis. The most common diag- noses on CNB/FNA were pleomorphic adenoma and metastatic squamous cell carcinoma. A Fisher’s exact test did not show a sta- tistically significant difference in the accuracy of CNB and FNA, this may be due to the limited sample size of the FNA group. Conclusion: CNB and FNA are both non-invasive techniques in comparison to a conventional biopsy and are often utilised in the head and neck region. The accuracy of these techniques presented here is similar to those previously reported in the lit- erature, approximately 90% for CNB and 70% for FNA. However, where previous studies found CNB to be more accurate than FNA this difference was not observed in this cohort. This may be due to the limited sample size of the FNA group. PS-02-013 Transcription factors profile in sinonasal neuroendocrine neo- plasms (snNENs) and olfactory neuroblastoma (ONB) F. Pettenon*, C. Facco, A.M. Chiaravalli, M. Turri-Zanoni, P. Castelnuovo, S. La Rosa, M. Cerati, F. Sessa, S. Uccella * Università degli Studi dell’Insubria, Department of Anatomical Pathology, Varese, Italy Background & objectives: snNENs are rare and mostly include neuroendocrine carcinomas (NECs). ONB is a unique sinonasal neoplasm, expressing neuroendocrine markers. We aimed to inves- tigate transcription factors expression profile in snNENs and ONBs and to explore their role in distinguishing these two entities. Methods: GATA3, SATB2 and CDX2 expression were investigated in a series of 26 ONBs and 7 snNENs diagnosed and treated in our Institution. ONBs were graded according to Hyams’ system (2 grade 1, 13 grade 2, 8 grade 3 and 3 grade 4) and epithelial NENs were reclassified into 5 NECs, 1 mixed neuroendocrine/non- neuroendocrine neoplasms (MiNENs) and 1 amphicrine carcinoma. Results: Hyams’ grade 1-3 ONBs stained diffusely and intensely for SATB2. Grade 4 ONBs and NECs were globally negative, including the NEC component of the MiNEN. The intestinal- type adenocarcinoma (ITAC) component of the MiNEN, like the amphicrine carcinoma, was intensely positive. GATA3 was heterogeneously expressed in Hyams’ grade 1-3 ONBs, whereas grade 4 ONBs, all NENs and the amphicrine carcinoma were completely negative. CDX2 was only expressed in the amphicrine carcinoma and, as expected, in the ITAC component of the MiNEN. Conclusion: Our study expands the spectrum of SATB2 and GATA3-positive neoplasms and identifies, for the first time, SATB2 and GATA3 expression as features of Hyams grade 1-3 ONBs, suggesting that Hyams grade 4 ONBs are not only clinically but also biologically different from low graded ONBs. These results are useful in diagnostic daily practice, as highlight that the joudicious employment of transcription factors may help in correctly diagnosing rare but clinically relevant neoplasms. PS-02-015 Cervical lymph node extemporaneous assessment by confocal microscopy during surgery: an alternative to frozen section examination? O. Casiraghi*, A. Villard, A. Aupérin, I. Breuskin, S. Asmandar, M. Abbaci *Gustave Roussy Cancer Campus, France Background & objectives: To evaluate the value of the Ultra-fast Confocal Microscopy (UFCM) imaging of cervical lymph nodes in S72