ECP 2023 Abstracts

S73 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 comparable (if slightly higher) than those from published clinical trials. More than 75% of cases were reported in 10 days, as per the department’s policy. Conclusion: The KEYNOTE-048 trial found 85% of cases had a CPS of 1 or more which is exceeded by our local ‘real life’ rate of 92%. Our local PD-L1 positivity rates for head and neck squamous cell carcinoma were comparable to those in published clinical trials. Turnaround times were similarly deemed to be satisfactory. PS-04-013 Nodular fasciitis of parotid gland: an uncommon lesion and a mimic of pleomorphic adenoma - a case series S. Naresh Shah*, S. Kar *Apollo hospitals, India Background & objectives: Nodular fasciitis (NF) is a self-limiting, pseudosarcomatous process composed of fibroblasts and myofibro- blasts. It commonly affects the upper extremity, head and neck region and lower extremity. Uncommon in parotid gland it mimicks pleomor- phic adenoma (PA) cytologically. Methods: We retrieved cases of NF of parotid gland from the labora- tory interface system from 2016 to 2021 in Apollo hospital, Chennai, India. Results: We report 8 cases of NF of parotid gland. The age of the patients ranged from 4 to 72 years, with male preponderance. Fine nee- dle aspiration (FNA) was performed in 6 cases which was followed up by biopsy. A diagnosis of PA was made in 3 cases on cytology, which turned out to be NF on histology. Subsequent cases raised a suspicion of NF on cytology itself, which was confirmed by histopathological examination. Two cases did not have cytological evaluation and were excised with a clinical diagnosis of PA. Conclusion: NF is a self -regressive benign lesion which can be left alone or treated by conservative surgery. It can mimic PA and few other benign and malignant lesions cytologically. We report these cases to familiarize the practicing pathologists with this entity, with a special emphasis on the importance of cytological analysis of these lesions, so that a presurgical diagnosis of NF may be rendered and unwarranted surgeries be avoided. PS-04-014 Tumour immune microenvironment in odontogenic carcinomas K. Oh*, S. Cho, J. Lee, H. Yoon, S. Hong *Dankook University, Republic of Korea Background & objectives: This study aimed to investigate the tumour immune microenvironment in odontogenic carcinomas and ultimately determine the applicability of immunotherapy as a novel therapeutic strategy and the prognostic significance of immune markers in patients with odontogenic carcinomas. Methods: The expression of T-cell markers including CD3, CD8, and FOXP3 was visualized by immunohistochemistry in 21 tissue samples of odontogenic carcinomas. Immune profiles were determined for each tumour type, and the density of T-cell subsets was calculated based on their spatial distribution. The associations of these immune markers with clinicopathological factors were statistically analysed. Results: 57.1% (12/21) of the cases studied were the immune-inflamed phenotype, which was defined as the presence of T cells in the tumour parenchyma. Among tumour types, the frequency of the immune- inflamed phenotype was highest in ameloblastic carcinoma (87.5%; 7/8) and lowest in clear cell odontogenic carcinoma (25.0%; 1/4). The densities of CD3+ and CD8+ T cells were significantly higher in the stroma than in the parenchyma (both, P < 0.001), and no correla- tions were observed between the densities of intratumoral and stromal CD3+, CD8+, and FOXP3+ T cells (all, Pearson correlation coefficient < 0.3). The intratumoral CD8+/CD3+ cell ratio was inversely associ- ated with tumour size (P = 0.048). Conclusion: Taken together with the results of our previous study on PD-L1 expression in odontogenic carcinomas, this study further supports the therapeutic potential of immune checkpoint blockade in patients with odontogenic carcinomas, especially in those with advanced ameloblastic carcinoma. Among T-cell subsets, the immune response by intratumoral CD8+ T cells may primarily inhibit tumour progression in odontogenic carcinomas. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. RS-2023-00212868). PS-04-015 Diagnostic algorithm for salivary gland carcinomas B. Othman* *Charles University, Czech Republic Background & objectives: The newly emerging salivary gland carci- nomas (SGC) have demonstrated diverse differentiation, while specific molecular mutations have been verified in a few neoplasms We propose a diagnostic algorithm that is based on molecular and immunohisto- chemical findings for each salivary gland carcinoma. Methods: After mining the medical literature for all SGCs published from 2015, we annotated each SGC for the marker(s) used and the level of evidence attained for diagnosing each published case. Question- able diagnoses were discarded. All SGCs were converted into nodes to which immunohistochemical markers were aligned to the right while molecular investigations were aligned to the left for clustering computationally. Results: We proposed a diagnostic algorithm a diagnostic that is based mainly on morphologic features and immunohistochemical investiga- tions and supported by molecular analysis. The generated results were compared to the findings retrieved from a reliable registry in which 1428 cases were diagnosed molecularly (using FISH analysis next- generation sequencing, PCR or a mixture of all). The accuracy of the diagnostic algorithm was 92%. The proposed algorithm was illustrated as a flowchart, which combines the use of principal immunohistochem- ical markers (IHC), complimentary ones and confirmatory molecular investigations. The SGCs which could be diagnosed with the listed markers were labeled for further consultation with expert pathologists. Conclusion: Our algorithm helps with diagnosing 19 SGCs, which pre- sent either monomorphous neoplastic spindle cells (e.g., myoepithelial carcinoma), biphasic populations (e.g., adenoid cystic carcinoma) or more (e.g., mucoepidermoid carcinoma). It also covers the morphologic features, including cellular differentiation (e.g., clear cells or oncoyctes), growth patterns (e.g., cribriform or mucinous), and high-grade transfor- mation (e.g., dedifferentiation and undifferentiation). It also highlights some markers whose expression could distinguish malignancies arising in benign lesions (e.g., Warthin-like mucoepidermoid carcinoma) from benign neoplasms masquerading as malignancies. PS-04-016 Effect of SMARCA4 in anaplastic thyroid cancer C. Wang*, U. Bhawal, H. Okada *Department of Histology and Embryology, Nihon University Graduate School of Dentistry at Matsudo, Japan Background & objectives: Anaplastic thyroid cancer is one of the most aggressive and deadliest malignancies. This study aimed to inves- tigate the biological roles and underlying molecular mechanisms of SMARCA4 in anaplastic thyroid cancer. Methods: Western blot analysis, transwell assay, flow cytometry and quantitative real-time PCR has been carried out to evaluate the changes