ECP 2023 Abstracts

S114 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 PS-17-040 Cost effectiveness of Helicobacter Pylori testing in gastric biopsies P. Tilekar*, K. Robertson, M. Elgoweini *Pathology department, University Hospital Crosshouse, United Kingdom Background & objectives: The Royal College of Pathologists guide- lines do not support biopsy of normal stomach or gastritis for histo- logical categorisation as neither is likely to change management. Here we estimate cost and efficacy of histological detection of Helicobacter pylori in our department. Methods: An electronic search was made of our departmental database for gastric biopsies received in November 2021. Clinical information such as presenting symptoms, endoscopy findings, clinical request for histological detection of Helicobacter pylori, histopathology diagnosis, number of glass slides and paraffin blocks were collected from clinical portal and Winpath systems. The cost was calculated. Results: Clinicians requested histological detection of H pylori in 53 (28.3%) out of 187 gastric biopsies received. 10 of these were endo- scopically normal while 43 had gastritis. Histologically, Helicobacter pylori was only detected in two biopsies; one from each group. 52 cases had one paraffin block processed and one had two. 51 cases had one glass slide while two had two glass slides processed. The labora- tory costs for the 53 cases were £1761.69. This included the cost of receiving, processing, embedding, cutting, staining, quality check and immuno-histochemistry. The cost of the consultants reporting time was £1176. Therefore, the total cost was £2937.69. Conclusion: The estimated cost for a diagnostic endoscopy is £398, making the cost of detecting two cases of Helicobacter pylori infec- tion, in our lab, for one month £24,031.69. Other, non-invasive tech- niques, such as faecal antigen testing or urea-breath testing, with com- parable sensitivity and specificity, are likely to be cheaper and safer alternatives. PS-17-041 Clinicopathological significance of LAG3+ immune cells in gastric cancer D. Ulase*, H. Behrens, S. Krüger, C. Röcken *Department of Pathology, CAU / UKSH Campus Kiel, Germany Background & objectives: Lymphocyte activation gene 3 (LAG3) is an immune checkpoint that is linked to T-cell exhaustion within tumour microenvironment. This study analysed spatial distribution of LAG3+ immune cells in relation to clinicopathological data in a set of 441 therapy-naive gastric cancers. Methods: LAG3 expression was evaluated in tumour centre (TC) and invasive front (IF) using immunohistochemistry and whole-slide digi- tal image analysis using Definiens Tissue Studio. Cases were divided into LAG3-low and LAG3-high groups based on median LAG3+ cell density. Associations with clinicopathological variables were analysed using cross-tabulation analysis and Kendall’s tau test for ordinal vari- ables or Fischer’s exact test for non-ordinal variables. Results: Median density of LAG3+ cells differed significantly between both compartments (p<0.001): 55.15 cells/mm2 in TC (range 3.57– 1687.63) vs. 70.35 cells/mm2 in IF (1.91–1858.35). Patients with high LAG3 expression at IF were more likely males (56.3% vs. 39.6% females, p=0.002) with proximally located tumours (58.5% vs. 46.2% distal, p=0.025). LAG3+ cell density at both compartments correlated with Lauren phenotype (p=0.001, TC; p<0.0001, IF) and was inversely associated with tumour budding (p=0.004, TC; p<0.0001, IF). Higher LAG3 expression correlated with EBV-positive (p<0.0001, both com- partments) and microsatellite instable (p=0.003, TC; p=0.005, IF) can- cers. Tumours with lower LAG3+ cell infiltration in TC tended to have advanced pT (p=0.075) and pN (p=0.079) categories. Conclusion: Our findings demonstrate differences in tumour micro- environment of the main histological and molecular subtypes of gastric cancer. Inverse relationship between LAG3+ cell density and tumour microinvasion (as demonstrated by budding) suggests that LAG3 expression could rather be a sign of crosstalk between can- cer and immune cells than a sign of exhausted, dysfunctional T cells. Our results support the need for extended analysis of both LAG3 and microenvironment of IF, as it appears to be more active compartment in gastric cancer. PS-17-042 Biological background of colorectal polyps and carcinomas with heterotopic ossification A. Vos*, L. Pijnenborg, S. van Lent-van Vliet, L. Kodach, F. Ciompi, C.S. van der Post, F. Simmer, I. Nagtegaal *Radboud University Medical Center, Nijmegen, The Netherlands Background & objectives: The molecular and cell biological mecha- nisms and the prognostic impact of heterotopic ossification in neo- plasms is not fully understood. This study will generate insight into the potential pathway by which heterotopic ossification develops in colorectal neoplasms. Methods: Via the Dutch nationwide Pathology databank 77 cases were collected. A literature search yielded an additional 96 case reports. Clinicopathological characteristics and several histological traits were scored for all these cases. To investigate the involvement of the TGFβ/ BMP pathway, our cases were stained immunohistochemically for BMP2, SMAD4, and Osterix. Using an artificial intelligence algorithm, the tumour-stroma ratio was determined. Results: The polyps consisted mainly of juvenile polyps (25%), tubu- lovillous adenomas (25%), and traditional serrated adenomas (25%). The carcinomas comprised mostly conventional (62.9%) and mucinous adenocarcinomas (32.3%), with a few serrated adenocarcinomas (4.8%). Many of the neoplasms showed fibrosis, both surrounding bone as in other parts of the tumour. Immunohistochemistry for BMP2, SMAD4, and Osterix frequently showed a gradient with more pronounced expres- sion in tumour and/or stromal cells directly surrounding bone. Eighteen cases (26.9%), showed such a gradient in two or more stains, indicating activation of the BMP pathway. The tumour-stroma analysis classified more than half of the cases as the mesenchymal subtype (CMS4). Conclusion: Heterotopic ossification is seen often in serrated and mucinous tumours as well as in juvenile/inflammatory polyps. Based on the enrichment of fibrosis, CMS4 and the observed staining patterns, it seems likely that induction of bone formation is due to activation of the BMP pathway. PS-17-043 Prognostic significance of tumour budding, desmoplastic reaction, and lymphocytic infiltration in patients with gastric adenocarcinoma A. Yavuz*, K. Şimşek, A. Alpsoy, B. Altunay, E. Ocak Gedik, B. Ünal, C.I. Bassorgun, A.M. Tatli, G.Ö. Elpek *Akdeniz University Department of Pathology, Turkey Background & objectives: In gastric adenocarcinoma (GAC), the rela- tionship among tumour budding (TB), desmoplasia, and the tumour microenvironment remains unclear. This study aims to determine the correlation among TB and desmoplasia and lymphocytic infiltration in patients with GAC and their impact on prognosis. Methods: Our study group consisted of 101 patients diagnosed with GAC. TB was defined according to the International Tumour Budding Consensus Conference (ITBCC). Desmoplastic reaction (DR) was clas- sified into three groups based on the maturation of tumour stroma. The evaluation of TIL was determined semi-quantitatively based on a 5% cutoff value. Statistical analysis was performed using SPSS version 27. Results: In our study group, peritumoral budding (PTB) was strongly correlated with intratumoral budding (ITB) (r: 0.970). Immature DR and low TILs were more frequently observed in tumours with high PTB