ECP 2023 Abstracts

S206 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 described: paediatric and adult-onset types. In paediatric-onset CG colla- gen deposition is generally restricted to the stomach; our paediatric patient also had no collagen deposition in duodenum or colon. CG is a rare entity; responds well to iron supplementation treatment therefore, possibility of CG should be considered in patients with persistent anaemia. E-PS-06-052 Microsatellite instability in ampullary adenocarcinoma V. Kropelnytskyi*, V. Shkarban, I. Romasko, I. Grygorova *Shalimov National institute of surgery and transplantation, Ukraine Background & objectives: Ampullary cancers make up to 6-9% of the pancreaticoduodenal zone tumours. The most frequent histology type is adenocarcinoma. Some cases are associated with microsatel- lite instability (MSI). The study aim is to evaluate MSI frequency in ampullary adenocarcinoma cases. Methods: The study included 69 patients who underwent pancrea- toduodenectomy for ampullary invasive adenocarcinoma during the period 2019-2022. TMA with core size 2 mm were constructed in man- ual mode. Immunohistochemistry for DNA mismatch repair proteins (MLH1, PMS2, MSH2, MSH6) were performed. Cases with preserved expression of all proteins were MSS. Cases with absence of expression of some proteins were considered as MSI. Results: MSI were detected in 9 out of 69 cases (13,8%). All of themwere MLH1/PMS2-defficient. Patients average age was 59.7±8.2 years for MSI cases and 61.1 ± 8.1 years for MSS cases. Intestinal type adenocarcinoma was in 5 cases (55.6%), pancreatobiliary adenocarcinoma was in 4 cases (44.4%). MSI cases more frequently have poorly differentiated morphol- ogy: 33.3% vs 14.2% in MSS cases. 2 out 5 intestinal adenocarcinoma cases have focal medullary morphology. Regional lymph nodes status for MSI cases was next: pN0 - 2 cases, pN1 – 6 cases, pN2 - 2 cases. Conclusion: MSI frequency in ampullary adenocarcinoma according to our data is 13,8%. Which is just a little less than generally accepted MSI frequency in colorectal cancer (15%). All the MSI cases were due to MLH1/PMS2-defficiency. Further research is needed to clarify whether it is sporadic or germinal microsatellite instability. Given that MSI cases in general have specific follow-up and treatment options, it is advisable to test ampullary adenocarcinoma for microsatellite instability. E-PS-06-053 Frequency of Her-2/neu positivity in ampullary adenocarcinoma V. Kropelnytskyi*, V. Shkarban, I. Romasko, I. Grygorova *Shalimov National institute of surgery and transplantation, Ukraine Background & objectives: Her-2/neu expression is most frequently found in breast and gastric cancer cases. According to the literature some ampullary adenocarcinoma cases also could have Her-2/neu overexpression. The study aim is to evaluate Her-2/neu overexpres- sion frequency in ampullary adenocarcinoma. Methods: The study included 69 patients who underwent pancreatodu- odenectomy for ampullary invasive adenocarcinoma during the period 2019-2022. TMA with core size 2 mm were constructed in manual mode. Immunohistochemistry for Her-2/neu was performed. Expres- sion was assessed based on the Her-2/neu gastric cancer guideline. Results: Her-2/neu overexpression with the expression degree 2+ and 3+ was detected in 2 out of 69 cases (2.8%). Case with 3+ expression degree has strong complete staining in 100% of tumour cells. Both were intestinal type adenocarcinoma, lymph node negative, pMMR (MSS). Conclusion: Her-2/neu overexpression rate in ampullary adenocarci- noma according to our data is 2.8%. According to different papers this rate is from 0 to 23%. Nowadays Her-2/neu testing is not included into standard diagnostic protocol for ampullary cancer. But considering the literature data (case reports) on the HER2-directed therapy effective- ness in cases of ampullary adenocarcinoma, it is advisable to consider this diagnostic option for metastatic cases. E-PS-06-054 Imunohistochemical study of morphologic impact of microsatellite instability (MSI) in malignant colorectal cancer (CRC) of local population M. Kupryte*, T. Navickis, N. Cesana, L. Poškienė *Lithuanian university of health sciences, Institute of Cardiology, Lithuania Background & objectives: CRCs with detected MSI have distinctive morphology. Study of CRC with MSI focusing on local population- associated morphological tendencies may present clinically relevant information optimizing individualized treatment in local healthcare infrastructure. Objective - identify population-focused morphologic tendencies among CRC with MSI. Methods: 100 cases were included in study and analysed according to parameters of CRC anatomical site, histological type, differentiation grade (G) of CRC, T and N stages of TNM classification, and MSI sta- tus (MLH1, MSH2, MSH6, and PMS2). Cases with selected CRC were classified into MSI and microsatellite-stable (MSS) groups. Statistical analysis of χ 2 test was applied (p<0.05). Results: Most of selected CRCs were diagnosed as infiltrative adeno- carcinoma (not otherwise specified, n=81, 81%), mostly of T3 stage (n=95, 95%), N0 stage (n=93, 93%), and of G2 (n=92, 92%). 30% of selected cases (n=30) had MSI status with predominant loss of MLH1 and PMS2 expression (both – 25% of MSI-associated CRCs) and BRAF expression (74% of MSI-associated CRCs, χ 2=21.754, p=0.001). MSI-associated CRCs were more likely to originate in ascending colon (n=11, 11%, χ 2=16.826, p=0.01) and have G3 (n=5, 5%, χ 2=6.5, p=0.039). No statistically significant features were detected in MSI-associated CRC group, when evaluating histological CRC type ( χ 2=9.259, p=0.16), T ( χ 2=1.365, p=0.505), and N stages ( χ 2=2.586, p=0.764) of TNM classification. Conclusion: Immunohistochemical study of morphologic impact of MSI in local population revealed that immunohistochemically diag- nosed MSI-associated CRC are more likely to loose MLH1 and PMS2 expression, originate in ascending colon, and have G3, representing worldwide tendencies of CRC morphology and its MSI status. E-PS-06-055 Gastrointestinal stromal tumour case report series and evaluation of prognostic parameters E. Kussever*, T. Toyran, E. Kilic Bagir, A. Acikalin *Cukurova University, Turkey Background & objectives: Gastrointestinal stromal tumours (GISTs) are the most common mesenchymal tumours of the gastrointestinal tract. They mostly derive from precursors of the interstitial cells of Cajal. We aimed to focused on pathological findings and prognostic parameters on GISTs. Methods: Totally 174 patients biopsy-proven GISTs were enrolled into this study between the years of 2012-2022 retrospectively. The effects of tumour size, localization, immunohistochemical markers, gender, histologic type and risk assessment and mitotic rate on prognosis were examined. Logistic regression analysis (forward method) and chi- square test were used in this study. A value of p<0.05 was considered statistically significant. Results: Patients were summarized as: the mean age was 59,34 years old, male/female ratio was 1. They were morphologically spindle cell (n:154), epithelioid (n:10) and mixed type(n:10). According to the risk assessment guideline, the risk was evaluated as no risk (n:15),very low (n:15), low (n:34), moderate (n:22) and high (n:88).There was no statistically significant relationship with gender (p:01) and tumour size (p:0.07).The prognosis was found to be better located in the GI tract than the other locations. ‘No risk’ and ’high risk’ groups had worse prognosis. We consider that the high mortality rate in the ’no risk’