ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 Methods: Immunohistochemical analysis was performed on a total of 23 patients with CRC and 18 adjacent normal tissues. Membra- nous expression of CD4, CD8 and nuclear expression of FOXP3 were analysed in T cells infiltrating the tissues in three different fields of the stained slides. Clinico-pathological characteristics were recorded. Results: Patients mean age range was 63.9 years. CD4, CD8 and FOXP3 markers were significantly expressed in CRC tissues compared to normal tissues (Mann Whitney U test: CD4 p=0,0034 ; CD8 p<0,0001 ; FOXP3 p=0,0019). Interestingly, high percentage of CD8 positive expression was reported in CRC (near 30%) compared to CD4 and FOXP3 (not exceeding 4%) suggesting a high cytotoxic T cell infiltration. CD8high expression was found mostly in CRC without perineural invasion versus those with perineural invasion (p=0.042). Conclusion: Altogether, our results showed the high expression of T cells infiltrating the tumour in CCR. Perineural invasion should be taken into consideration to design crucial strategies for CRC treatment. PS-07-009 HLA-E proteins expression and clinical relevance in colorectal cancer N. Boujelbene, I. Zemni, S. Dhouioui*, H. Ben Yahia, W. Babay, M. Brahim, H. Ouzari, K. Mrad, I. Zidi *Laboratory Microorganismes and Active Biomolecules, Sciences Faculty of Tunis, Tunisia Background & objectives: Human leukocyte antigen(HLA)-E is a non-classical HLA class I molecule implicated in immune cells modulation. Many studies proposed HLA-E molecule as a predictive biomarker for cancers’ outcome. We aimed to characterize the HLA-E expression in colorectal cancer(CRC) according to clinicopathological characteristics. Methods: HLA-E expression was studied in tumour tissues and adjacent normal tissues from 22 CRC patients by immunohisto- chemistry. HLA-E expression was found at the surface of cells. Labelled tumour cells percentage determined semi-quantitatively was correlated to clinico-pathological parameters. Results: Patients mean age range was 64 years. HLA-E expression was significantly expressed in CRC tissues compared to normal tissues (100% and 86.6% respectively; Mann-Whitney U test: p < 0.0001). Moreover, high expression of HLA-E was revealed in patients exceeding 63 years, in those with early tumour stages (stage I and II), in those without lymph nodes metastasis, and in those with well differentiated tumours without significance. Conclusion: Our results suggest that HLA-E is implicated in CRC promotion and could be proposed as a candidate biomarker for CRC. Its prognosis value remains to be confirmed through a wider study population. PS-07-010 Epstein-Barr virus infection in chemoradiotherapy-naïve gastric adenocarcinoma: relationship with PD-L1 Expression and survival F. Sassi, R. Jouini, K. Ben Lazreg*, I. Helal, F. Khanchel, R. Hed- hli, H. Zaafouri, M. Sabbah, O. Khayat, E. Ben Brahim, A. Chadli *Habib Thameur Hospital Pathology department, Tunisia Background & objectives: EBV has emerged as a prognostic biomarker in gastric adenocarcinomas (GA). EBV associated GA (EBVaGA) accounts for 10% of GA and comprises amplification of PD-L1.We aimed to assess EBV status and PD-L1 expression in GA with clinicopathological features and survival. Methods: We performed tissue microarray slides from 143 GA patients treated with radical gastrectomy. PD-L1 expression was evaluated through immunohistochemistry (Combined Positive Score ≥1) and EBV status through chromogenic in situ hybridiza- tion. Differences in overall survival (OS) were assessed using the Kaplan-Meier method, log-rank test and Cox proportional hazards regression model. Results: EBVaGAs accounted for 33.6%. They were associated with male gender (70.8%; p=0.020). The tumours were in the antrum (54.2%) with tumour size > 6 cm (52.2%). According to WHO classification, they were classified as poorly cohesive adenocarcinomas (43.8%). According to Lauren classification, they were classified intestinal subtype (45.8%), diffuse (43.8%) and indeterminate (10.4%). Perineural invasion was observed in 68.8% of cases and vascular emboli in 85.4%. EBVaGAs were associated to pT1/pT2 stage (p=0.031), low rate of lymph node metastasis (p=0.029) and PD-L1+ status (p=0.016). EBV+ status was predictor to PD-L1+ status (p=0.018). Median survival was 17 months in patients with EBVaGA compared to 16 months in EBV negative GA. Conclusion: The prevalence of EBVaGA is high in Tunisian popu- lation (33.6%). It is more frequent in poorly cohesive than tubular adenocarcinomas. EBVaGAs were more common in the antrum which does not fit reports in the literature. EBV+ status was a predictive factor to PD-L1 expression which suggests that patients infected with EBV may respond to PD-1 checkpoint inhibitors. This incites to further investigation of EBV carcinogenesis for therapeu- tic targets to select high-risk patients. PS-07-011 Ckit mutations in patients with gastrointestinal stromal tumours M. Ramadwar*, L. Rambadran, O.S. Shetty, M. Gurav, K. Deodhar, M. Bal, R. Kaushal, S. Yadav, V. Ostwal, M. Bhandare *Tata Memorial Hospital, India Background & objectives: CKIT mutations are oncogenic drivers for gastrointestinal stromal tumours (GISTs). They also function as predictive markers for response to imatinib. We studied various histologic types of GISTs, risk stratification, types of Ckit mutations and correlated with survival. Methods: Histology and immunohistochemistry of 98 patients diagnosed with GIST were reviewed retrospectively. Histologic risk stratification was derived using CAP protocol. Sequencing results for Ckit exons 9,11, 13 and 17 were documented. Histologic and molecular parameters were correlated with survival. Clinical data was derived from electronic medical records. Results: Immunohistochemistry for Ckit and DOG1 was positive in 98% of tumours; 2% being positive for DOG1 only. The histo- logical risk groups were not associated with statistically signifi- cant differences in PFS (p=0.6) or OS (p=0.7). Ckit mutation rate was 73%, Exon 11 mutations were found in 75% of patients, exon 9 in 19%, exon 13 in 4.1 % and exon 17 in 5.5 % respectively. All patients with exon 9 mutations had consistent duplication c.1504_1509dupGCCTAT. Decision of dose escalation of imatinib or change to second line TKI was made in all patients with ckit exon 9 mutation. No statistical difference could be demonstrated among different mutational types when correlated with survival. Conclusion: Overall Ckit mutation rate was lower (73%) than reported in literature, thus concluding that incidence of ckit muta- tions could be lower in Indian population. Ckit exon 9 mutations had consistent duplication while deletions and substitutions were found in in exon 11. Exon 9 mutations guided treatment decisions. However, no statistical difference could be demonstrated among histological risk stratification and different mutational types when S93