ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 J. Jeong*, U. Jo, K. Cho, J.S. Song *Department of Pathology, Asan Medical Center, Republic of Korea Background & objectives: Programmed death ligand 1 (PD-L1) expression is predictive biomarker for immune checkpoint inhibitor in head and neck squamous cell carcinoma. We compared the vari- able immunohistochemical (IHC) assays using the tumour propor- tion score (TPS) and the combined positive score (CPS). Methods: In total 56 cases of head and neck carcinoma (HNC), PD-L1 expression was evaluated for formalin fixed paraffin embed- ded (FFPE) blocks from biopsy and surgical resection specimens using 4 IHC assays including 22C3 pharmDx on the Dako Link 48 platform and on Ventana Benchmark Ultra platform, SP263, and SP142 by TPS and CPS using cut-offs of >1% and >50%. Results: Overall PD-L1 positivity rates were 83.9% (47/56) with a cut-off ≥1% and 21.4% (12/56) with a cut-off ≥50%. The average of TPS scores were 18.03 ±24.83 with 22C3 on Ventana assay, 16.56±25.84 with 22C3 pharmDx, 16.76± 25.16 with SP263 assay, and 3.72±11.48 with SP142 assay, resulting in the lowest expres- sion rate in SP142 assay. A statistically significant correlation (p=0.012) was analysed between location and PD-L1 expression using a cut-off ≥50%. When comparing different assays, 22C3 pharmDx and SP263 assay using TPS score showed good correla- tion with Spearman correlation coefficients calculated as 0.892 (p <0.001). However, less agreements were observed among 22C3 pharmDx, SP263 assay, and SP142 assay. Conclusion: Overall PD-L1 positivity rate with a cut-off ≥1% was 83.9%. PD-L1 expression was statistically significant correlation with the location (P = 0.012). The correlation of PD-L1 expression between paired the biopsy and resection specimen is evaluating in this ongoing research. PS-02-008 PD-L1 expression and its clinicopathological significance in odontogenic carcinomas K. Oh*, J. Kim, S. Cho, J. Lee, H. Yoon, S. Hong *Seoul National University, Republic of Korea Background & objectives: Programmed cell death-ligand 1 (PD- L1) expression has been investigated in various malignancies and is currently used for immunotherapy selection in patients with several cancers. This study aims to primarily identify PD-L1 expression and determine its clinicopathological significance in odontogenic carcinomas. Methods: PD-L1 (clone E1L3N) immunohistochemistry was per- formed in 20 odontogenic carcinomas after validated compared to the 22C3 pharmDx assay. The percentage of tumour cells with membranous staining at any intensity (TPS) ≥ 1% was defined as PD-L1-positive. Associations between PD-L1 expression and clinicopathological factors were statistically analysed. Results: PD-L1 was positively expressed in 85.7% (6/7) of amelo- blastic carcinomas, 37.5% (3/8) of primary intraosseous carcino- mas, 33.3% (1/3) of clear cell odontogenic carcinomas, and 50% (1/2) ghost cell odontogenic carcinomas. Positive PD-L1 expres- sion was associated with larger tumour size (P = 0.031), whereas no correlation was observed with age, sex, and tumour location (P > 0.05). Most cases (3/4; 75.0%) of odontogenic carcinomas with metastasis showed high PD-L1 expression (TPS ≥ 50%). Conclusion: These results suggest the possible utility of immune checkpoint inhibitors for the treatment of patients with advanced odontogenic carcinomas, which warrants further clinical investigation. PS-02-009 Assessment of TP53 and CDKN2A status can be a predictive marker of malignant transformation of sinonasal inverted papilloma S. Kwon*, E.S. Kim, J.H. Paik, J. Chung, J.H. Wee, S. Cho, T. Won, J. Kim, C.S. Rhee, H. Kim *Seoul National University Bundang Hospital, Republic of Korea Background & objectives: Sinonasal inverted papilloma (IP) has the potential to transform into squamous cell carcinoma (SCC), but there are no diagnostic methods to predict it. We investigated genetic mutations involved in progression of IP-SCC and explored biomarkers that can predict malignant transformation. Methods: 14 patients diagnosed with SCC arising in IP and six patients diagnosed with IP without malignant transformation were included. DNA was extracted from IP, IP with dysplasia, and SCC, respectively, and whole exome sequencing and immunohistochem- istry (IHC) was performed. Results: Major oncogenic mutations were observed with high fre- quency in the stepwise progression from IP to SCC. TP53 was the most frequently mutated gene (39%), followed by CDKN2A (27%), TTN (27%), ARID1A (21%), and PIK3CA (15%). Muta- tions in TP53 and/or CDKN2A were observed in 3 out of 6 IPs with malignant transformation, whereas none of the mutations were observed in IPs without malignant transformation. As a result of TP53 and CDKN2A IHC, three of six IPs with malignant trans- formation showed a diffuse strong or null pattern in p53, and one showed a total loss of p16 which is distinct pattern from pure IPs. Conclusion: Our result suggests that assessment of TP53 and CDKN2A status can be a predictive marker of malignant transfor- mation of IP and assessment of p53 and p16 status using IHC can be a surrogate marker for TP53 and CDKN2A status. PS-02-010 Ossifying fibroma of the jaws: a clinicopathological case series study M. Triki*, S. Makni, S. Graja, O. Boudawara, N. Gouiaa, W. Ghribi, T. Boudawara, R. Kallel *Department of Pathology, Habib Bourguiba University Hospital, Sfax, Tunisia Background & objectives: Juvenile trabecular ossifying fibroma (JTOF) and juvenile psammomatoid ossifying fibroma (JPOF) are two rare histological variants of ossifying fibroma (OF). Theses variants are 3 distinct clinicopathological entities. Our aim is to assess clinico-pathologic features of a case series of OF. Methods: Eleven consecutive cases of OF diagnosed in the department of pathology of Habib Bourguiba Hospital, were collected from 2011 to 2021. The clinical data and microscopic features of these cases were reviewed and analysed with the most recent diagnostic criteria for OF. Results: Patients mean age at diagnosis was 35 years with a sex- ratio of 0,2. Eight cases were found in the mandible and three in the maxilla. Bone swelling or expansion was the most frequent clinical presentation (90%). Microscopically there was 8 cases of classic OF comprised of globulous woven or lamellar bone with rare or without osteoblastic rimming mixed with fibrous tissue and three cases of JPOF comprised predominantly of psammoma bod- ies mixed with a highly cellular fibrous tissue. No case of JTOF was recorded. No cellular atypia or mitosis were identified. Recur- rences were recorded in two women with JPOF, aged 16 and 22 years respectively. These recurrences were surgically removed. Conclusion: OFs occur more frequently in female patients and in those in the second to fourth decades of life. The most commonly affected site is the mandible. Most OF can be treated S71