ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 cases were grouped as low stroma (<36%) and high stroma (≥36%) with a threshold value of 36% determined. The clinicopathological findings, recurrence, and survival data were compared with TSR. Results: According to this threshold value, 63.2% (n=98) of the cases had low stroma and 36.8% (n=57) had high stroma. A statistically significant negative correlation was found between TSR and overall survival, disease-free survival and recurrence rate (p:0.001; p<0.01). Of the clinicopathological parameters, only gender and perineural invasion (PNI) were found to be significantly associated with TSR (p=0.031; p<0.05). In Cox multivariable regression analysis, a significant statistical correlation was shown between overall survival and age, stroma ratio, histopathological subtype, LVI, and T stage (p<0.01). It was determined that tumour stroma ratio ≥36 increased the mortality risk of the cases by 2.253 (95% CI: 1.411-3.597) times. Conclusion: TSR has a strong, independent prognostic value in gastric adenocarcinomas and would therefore be considered for integration into routine pathology practice after evaluation in vali- dation studies with larger series. PS-07-035 Mismatch repair status and PDL-1 expression in gastric carcinoma Z. Bayramoglu, S. Yilmaz Erozbek*, E. Kuzucular, F. Özden *Istanbul Medipol University, Pathology Department, Turkey Background & objectives: Gastric cancer (GC) is the 4th most common cancer worldwide and the 2nd leading cause of cancer- related death. In our study, the relationship between microsatellite instability and programmed death-ligand 1 (PDL-1) expression in GCs and clinicopathological parameters was investigated. Methods: Immunohistochemical staining for PD-L1 (22C3 clone) expression was performed on 37 cases. Expression was scored in both the tumour and tumour-infiltrating immune cells. Furthermore, tumoral mismatch repair status (MLH1, MSH2, MSH6, PMS1) was evaluated. Results: Twenty of our patients were male and 17 were female. The mean age was 62.5 (range 34-87). PD-L1 expression, either tumoral or tumour-infiltrating immune cells, was present in 8,10% (3/37) of GCs. Overall mismatch repair deficiency was seen in 27,02% (10/37) of the cases. PDL1 expression was observed in all mismatch repair-deficient cases (3/3). Conclusion: We found PDL-1 positive in 30% of our patients with mismatch repair deficiency. Thus, gastric cancer patients with mismatch repair deficiency tend to show PD-L1 expression; this specifically indicated that mismatch repair deficiency could be prime candidates for PD-L1-directed therapy. Further studies in larger series are needed to confirm our findings. PS-07-036 Assessment of mucosal lymphatic vessels and regional lymph nodes of in-situ colorectal carcinoma M.T. Rodrigo, K. Saez De Gordoa*, I. Archilla, S. Lopez-Prades, N. Vidal-Robau, G. Caballero, R. López del Campo, L. Rojo, A. Diaz, M. Cuatrecasas *Pathology Department, Hospital Clínic, Barcelona, Spain Background & objectives: Lymph node (LN) metastasis is an important prognostic factor in colorectal carcinoma (CRC). We aimed to demonstrate the presence of lymphatic vessels (LV) in the mucosa of in-situ CRC (pTis), and the analysis of regional LNs using a molecular method. Methods: This is an observational and retrospective study of surgi- cally resected in-situ CRCs. of LNs were assessed with both the One Step Nucleic Acid Amplification (OSNA) assay and H&E. The OSNA result, or total tumour load (TTL), is the amount of CK19 mRNA copies present in all LNs from a patient. D2-40 immu- nostaining was performed in both pTis and normal mucosa. Results: We analysed 39 surgically resected in-situ CRCs. The mean age was 68.6 years-old, 23 (59%) were men, and 22 (56%) were located on the right colon. A median of 16 LNs were freshly dissected per patient. All cases were low-grade, pN0 with H&E and did not receive adjuvant therapy. At follow-up, all patients were alive without disease between 1 and 5 years. All tumours presented LVs in the lamina propria, being negative in normal colon mucosa. We detected 11/39 (28%) patients with positive LNs by OSNA. Positive tumours were more frequent in older men and located in the right colon. The TTL were low, from 400 to 4270 copies/μL. Conclusion: Despite of pTis is considered to have little or no risk of LN metastasis, this study demonstrates the presence of LVs in the lamina propria of in-situ CRC, and of low amounts of tumour burden in regional LNs, only detected by molecular methods. Nev- ertheless, this positivity has been demonstrated to confer no clini- cal significance or risk of recurrence. PS-07-037 The impact of cancer stem cell markers in distal cholagniocarinoma G. Fontinha*, J. Gama, F. Silva, P. Teixeira, R. Oliveira, M.A. Cipriano *Centro Hospitalar e Universitario de Coimbra, Department of Pathology, Portugal Background & objectives: Distal cholangiocarcinoma (dCCA) has a low incidence but exhibits a poor prognosis even in patients submitted to curative resection. This study sought to evaluate the prognostic value of cancer stem cell (CSC) markers in patients with dCCA, after surgical resection. Methods: Retrospective cohort study with evaluation of all patients submitted to surgical resection due to dCCA, between 2008 and 2019. The primary endpoint is to assess the value of CSC markers in overall survival (OS) and disease-free survival (DFS). Immunostaining for CD44, ALDH1 and CD56 was performed. The study was approved by the local Ethics Committee (CHUC-123-20). Results: 37 patients were identified, with 62.2% male and 37.8% female, with an average age of 69.19 (±9.92) years. After a median follow-up of 14±23.7 months, the OS was 16±2.8 months and the DFS was 14±5.2 months. CD44 and ALDH1 expression was observed in 34.8% and 26.1% of the evaluated tumours, respectively. No expression of CD56 was registered. In univariate analysis, CD44 (p=0.032) and ALDH1 (p=0.016) expression had inf luence in OS. Regard- ing DFS, no inf luence was verified. Multivariate analysis confirmed these findings: CD44 (HR=0.089, p=0.033) and ALDH1 (HR=9.24, p=0.037). ALDH1 expression was estab- lished as an independent worse prognostic factor concerning OS, with CD44 expression being associated with a better prognosis. Conclusion: This study supports the role of CSC markers as predictors of OS in dCCA. ALDH1 expression was associated with worse OS, which is related to the more aggressive biologi- cal behaviour of these cells. CD44 was unexpectedly associated with a better OS, which may be explained by the fact that in our study the majority of CD44 positive tumours were small and at an initial stage (T1/T2). More studies are needed to clarify this role. S100