ECP 2023 Abstracts

S111 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 tumour cells. Ki-67 index was counted for 500-1000 tumour cells in hot spots, median % of Ki-67 index is presented. Results: Average age was 54.7±12.6 years (median 55), 55 females, average tumour size – 3.16 cm (0.2-18 cm). 37/89 neoplasms located in the stomach body, 12 – in cardia, 11 – in antrum. In 29 cases the region was not specified. 79 cases were NETs G1-G3 (G1:G2:G3 – 51:24:4), 10 – NECs. Median Ki67 was for NETs G1 – 1.2%, G2 – 7%, G3 – 18; for NECs – 50%. PDX-1 was positive in 36/79 NETs: 27/51 G1, 6/24 G2, 3/4 G3. 7/10 NECs were PDX-1-positive. PDX-1 was positive in 24/31 GCs (13/13 signet-ring). Statistically significant relationship was shown between PDX-1 expression and the NEN grade (p=0.002). Conclusion: In our study, PDX-1 expression was most often detected in most G3 NETs, NECs and gastric cancers, especially in signet-ring cell car- cinomas. Our results indicate the important role of PDX-1 in the malignant transformation of the gastric epithelium and a possible target for treatment. PS-17-030 Colon neuropathy as a predictor of the development of diverticular disease V. Pechnikova*, L. Mikhaleva, A. Konyukova, A. Proshchina, O. Vasyukova, K. Bolikhov, A. Shulaev, N. Gutyrchik, A. Mikhalev, S. Shapovalyants *Avtsyn Research Institute of Human Morphology of Federal State Budgetary Scientific Institution "Petrovsky National Research Centre of Surgery", Russia Background & objectives: Diverticular disease is one of the most common diseases of the colon, however, the predictors of a compli- cated course have not been formulated. The aim of our study is to deter- mine the morphological predictors of the complicated diverticulosis Methods: We analysed 103 consecutive cases of left-sided hemicolec- tomy, 15 cases were studied comprehensively. Surgical specimens were fixed in 10% neutral buffered formaline and stained by hematoxylin- eosin and immunohistochemistry with S100 and b3-tubulin antibodies. Morphometric evaluation was performed in order to assess the glial index (the ratio of glial cells to neurons) in myenteric plexus of colon. Results: Among 15 extensively studied cases 6 patients (40.0%) had complicated diverticulosis of the colon, 5 (33.0%) presented with uncomplicated diverticulosis and 4 (27.0%) had no diverticula of the colon (comparison group). We noted an increase in the glial index in observations in patients with complicated and uncomplicated diverticu- lar disease (8.1), in contrast to the comparison group (6,4). However, there was no significant difference comparing the uncomplicated and complicated disease. Conclusion: The present study demonstrates that the glial index is significantly higher in patients with diverticular disease of the colon (8,1) than in the comparison group (6,4). Our results indicate that the glial index can be considered as a predictor of the development of diverticular disease, however, it is not possible to judge uncomplicated and complicated disease. PS-17-031 Assessment of intra- and intertumoural heterogeneity of molecular biomarkers in locally advanced gastric cancer G. Raskin*, N. Beliak, M. Mukhina, M. Kleshev, R. Orlova, S. Kutukova *Dr. Berezin Medical Insitute, Russia Background & objectives: Significance of intertumoral heterogeneity of biomarkers in gastric cancer are poor established. The aim of the study was to evaluate the heterogeneity of the main molecular biomark- ers in the primary tumour and in metastasis to the regional lymph node. Methods: A total of 62 patients with primary loco-regional (N+) gas- tric adenocarcinoma were recruited. The study included 20 women and 42 men. 44 patients had Laurén’s intestinal type of cancer, 18 had a diffuse type. One block with primary tumour and one with metastasis to the regional lymph node were selected for HER2, MMR, PD-L1, FGFR2 immunohistochemistry, FISH FGFR2, CISH EBV. Results: 10 patients (6,2%) showed overexpression of HER2/neu, and heterogeneity was detected in five cases. 4 patients showed dMMR (6,45%), in two cases heterogeneity in dMMR status was also revealed: it was presented in the primary tumour and absent in regional metas- tasis (pMMR). And in one case, heterogeneity in terms of dMMR was observed both in the primary tumour and in the metastasis. In 12 cases (19,6 %) marked heterogeneity in PD-L1 status between the primary tumour and its regional metastasis (1 case with dMMR heterogeneity) was also revealed. In one case FGFR2 gene amplification was detected in the primary tumour, which was "lost" in the metastasis. Conclusion: The findings in this paper indicates that the intertumoral heterogeneity of HER2 overexpression is common in GC patients. We highly recommend at least two samples for accurate HER2 assessment. Given the rarity of status detection dMMR, a study in a larger number of patients is required, however, our data also confirm the presence of heterogeneity in dMMR status, and probably the possibility of metas- tasis of a more aggressive pMMR clone. Heterogeneity in PD-L1 is not rare and has practical significance. PS-17-032 Expression and amplification of FGFR2 in gastric cancer: a com- parative study G. Raskin*, M. Mukhina, E. Kravtcova, I. Tsimafeyeu, S. Tjulandin, N. Beliak, M. Kleshev, R. Orlova *Dr. Berezin Medical Insitute, Russia Background & objectives: FGFR2 status in gastric cancer is an impor- tant factor in determining optimal treatment with FGFR2 inhibitors. The question remains how different assays agree on the FGFR2 status of the same patient and whether one test can be substituted by another. Methods: Pairwise comparison of 4 tests based on the same patient population was performed: 4 IHC assays [Abcam clone EPR24075- 418, R&D clone 98706, Santa Cruz clone C-8, Abcam 1G3] and one FISH test. 61 formalin-fixed, paraffin embedded samples (including 61 primary tumours and 61 metastases of same patients) were obtained and were stained with FGFR2 IHC assays. Results: After evaluating the expression in the first 16 patients, further study was carried out only using the Abсam EPR24075-418 assay due to pronounced nuclear staining with other IHC tests. FGFR2 any level expression was detected in 26 (43%) tumours. The prevalence of FGFR2 amplification was 8% and was accompanied by 3+ expression in 4 cases, 2+ - in 1 case. Discordance between FGFR2 expression in primary tumour and lymph node metastases was revealed in 13 (21%) cases. Conclusion: EPR24075-418 assay showed the best results among others in FGFR2 immunohistochemical evaluation: concordance with FISH was 100% in 3+ cases. Due to high FGFR2 heterogeneity in tumour, both pri- mary tumour and metastasis must be stained by immunohistochemistry or when it is not possible more material of primary tumour should be evaluated. PS-17-033 Evaluation of well-known and candidate tumour-agnostic biomarkers with molecular pathological alterations according to tumour localisa- tion in colorectal carcinoma: in silico analysis Z. Sağnak Yılmaz*, S. Demir Kececi, M.H. Toper, S. Sarioglu *Dokuz Eylül University, The Institute of Health Sciences, Department of Molecular Pathology, Karadeniz Technical University, Faculty of Medicine, Department of Pathology, Turkey Background & objectives: To determine the prognostic value of tumour agnostic markers in colorectal carcinoma (CRC) cases by in silico analy- sis and to evaluate their distribution in anatomical sub-regions of the colon and whether there are genomic differences in rectal carcinomas.