ECP 2023 Abstracts

S105 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 bowel adenocarcinoma (EO-SBA) are lacking. We aimed to investigate EO-SBA clinico-pathologic features. Methods: A retrospective study was conducted on an international multicentric cohort of 208 SBA patients. EO-SBAs (i.e., SBAs with age at cancer diagnosis <50 years) were compared to late-onset SBAs (LO-SBAs) (i.e., age at diagnosis ≥50 years) in terms of predisposing conditions (hereditary syndromes and immune-mediated disorders), other clinico-pathological features, and cancer-specific survival. Mis- match repair status was assessed by immunohistochemistry. Results: Forty-one EO-SBAs (mean age: 40 years; 20 males) and 167 LO-SBAs (mean age: 66.9 years, 109 males) were identified. A predis- posing condition was significantly more common in EO-SBAs (76%) compared to LO-SBAs (52%, p=0.008). Association with celiac disease, Crohn’s disease, familial adenomatous polyposis and Lynch syndrome was reported in 13 (32%), 13 (32%), 2 (5%), and 3 (7%) EO-SBAs, and in 28 (17%), 45 (27%), 0, 14 (8%) LO-SBAs, respectively. Among such predisposing conditions, only celiac disease proved to be significantly more frequent in EO-SBAs compared to LO-SBAs (p=0.047). No signif- icant difference was found between the two groups for remaining clinico- pathologic features, cancer-specific survival, or mismatch repair status. Conclusion: When compared to LO-SBAs, EO-SBAs showed a higher rate of cases associated with predisposing conditions, and the difference was mainly due to the association of EO-SBAs with celiac disease. The present study emphasizes the importance of assessing potential predisposing conditions in all EO-SBA patients. PS-17-008 Mucinous carcinoma: pathomolecular and microenvironment characterisation - a trans organ study M.A. Bani*, P. Dartigues, C. Genestie, M. Classe, A. Boileve, M. Ducreux, J. Scoazec *Department of Medical Biology and Pathology, Morphological pathology laboratory, Gustave Roussy Cancer Campus, Villejuif, France, Paris-Saclay university, Gustave Roussy Cancer Centre, Inserm US23, CNRS UMS3655, AMMICa, Villejuif, France Background & objectives: Mucinous carcinomas (MC) can arise in any type of epithelial tissue. Previous studies focused only on specific organs. This is a trans-organ study aiming to establish the molecu- lar profile and to reveal the different components of tumour immune microenvironment. Methods: Descriptive, retrospective and monocentric study on patients treated in our institution between 2015 and 2021 for MC. Clinical data were collected from medical records and histological samples re-exam- ined for histoprognostic factors. Tissue hypoxia in tumours and the pro- portions of immune cells were studied by immunohistochemical methods and digital image analysis. A molecular study was done by Next Genera- tion Sequencing. Results: The study involved 206 CM from 13 different organs. In the uni- variate study for overall survival: gender(male), size(>6cm), tumour site, vascular invasion, perineural invasion, signet ring cells, nodal invasion and T3/T4 TNM stages were significantly associated with poor prognosis. In the multivariate study, only perineural invasion (p=0.001) and T stage (p=0.018) remained statistically significant. More frequent mutations were found in the ERK-pathway (65.21%) and less frequently in TP53 (24%) and PIK3CA (15%). The highest hypoxia score was found in ovary and head and neck. There was a predominant infiltration by macrophages in the mucin and by T lymphocytes in the peri-tumoral areas. These fac- tors had no impact on overall survival. Conclusion: Our preliminary results do not show any significant differ- ence in the molecular profile of the sequenced MC as well as the compo- sition of immune infiltrates. Mutations on the ERK-pathway seem to be predominant in all different sites. We also demonstrate the spatial hetero- geneity of the immune microenvironment of MC in different organs. A significant difference in the hypoxia score between different organs could explain some different biology. PS-17-009 Small intestinal metaplasia in indefinite for dysplasia, dysplasia, and adenocarcinoma in patients with inflammatory bowel disease A. del Portillo*, A. Koehne de Gonzalez, L. Fazlollahi *Columbia University Irving Medical Center, USA Background & objectives: Recent studies show loss of the colonic marker SATB2 in inflammatory bowel disease (IBD)-associated dys- plasia and carcinoma. We tested whether this represents small intestinal metaplasia by examining these lesions for expression of SATB2 and other small intestinal markers. Methods: We searched for cases of IBD with dysplasia, carcinoma, and indefinite for dysplasia from 2010-2022. We tested 30 colon samples (biopsies and resections) from 26 patients with IBD with diagnoses of indefinite for dysplasia (6), low-grade dysplasia (10), high-grade dysplasia (8), and carcinoma (6) for the small intestinal markers CD10, HepPar1, and colon marker SATB2 by immunohistochemistry. Results: At least one marker of small intestinal metaplasia was seen in lesional cells in colon samples of 85% (11/13) of patients with high- grade dysplasia or carcinoma. CD10 was expressed in the lesional cells in 30% (9/30) of cases and in 35% (9/26) of patients. SATB2 was lost or showed reduced/patchy expression in 38% (11/29) of cases tested (one case was not stained) and 42% (11/26) of patients. HepPar1 was expressed in at least 47% (14/30) of cases (5 cases failed, 11 cases were negative in the lesion) and 50% (13/26) of patients. When SATB2 was lost/reduced, at least one other small intestinal marker was expressed in 82% (9/11) of cases/patients. Conclusion: IBD-associated dysplasia and carcinoma often exhibit small intestinal metaplasia. We previously found that small intestinal metaplasia occurs in non-neoplastic colonic mucosa from patients with IBD at a lower rate (5.3% CD10 expression, 13.8% HepPar1 expres- sion, 3.2% lost/reduced SATB2 expression). Thus, IBD-associated dysplasia enriches small intestinal metaplasia. These findings suggest that small intestinal metaplasia in colonic mucosa of patients with IBD may represent a marker of progression to IBD-associated dysplasia and carcinoma. PS-17-010 Prognostic value of tumour infiltrating lymphocytes in colon cancer S. Gharbi*, D. Bacha, I. Mallek, E. Benammou, M. Hajri, H. Mestiri, A. Lahmar, S. Ben Slama *Department of Pathology, Armand Trousseau Hospital-Sorbonne University, France Background & objectives: Tumour-infiltrating-lymphocytes (TILs) are currently considered as a prognostic factor in several cancers. For stageII colon cancer(CC), studies are underway to validate the prog- nostic value of this parameter. The objective of this study was to assess the prognostic value of TILs in stageII CC. Methods: It was a retrospective and descriptive study. It involved 70 patients, who underwent curative surgery for stage II colonic adenocar- cinoma. The data was collected over a period of 15 years with a mean follow-up of 24 months. Results: The mean age of the patients was 60years. The most fre- quent circumstances of discovery were abdominal pain (48%), fol- lowed by digestive tansit disorder(26%) and digestive bleeding(20%). All patients (n=51) at "high risk" of recurrence had received adjuvant chemotherapy except for seven patients. The mean overall survival and recurrence-free survival rates were 51 and 56 months, respectively. TILs rate varied between 3% and 80%. TILs rate <50% significantly decreased recurrence-free survival in univariate analysis (p=0.001). In multivariate analysis, it was identified as an independent factor for