ECP 2023 Abstracts

S202 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 of starting corticosteroid therapy, the case has been assigned to us. The duodenal biopsies received showed diffuse, marked inflammatory changes of chronic active duodenitis with subtotal villous atrophy. The luminal surface was covered by numerous spherical, basophilic mero- zoites. Despite the lack of cytomegalovirus cytopathic alterations, IHC studies for CMV have been performed and showed occasional nuclear staining in endothelial and epithelial cells. Conclusion: Following our histopathological report of cryptosporidi- osis and CMV duodenitis on a background of immunodeficiency, other tests have been performed and revealed an unknown HIV infec- tion in this case. Immunodeficiency should always be considered as a background for gastro-intestinal opportunistic infections. Whenever we identify one pathogen we should always ponder that there may be more. Knowing and acknowledging these specific microorganism- induced histological alterations provides us the ability of identifying the systemic cause and, therefore, establishing the proper treatment for immunocompromised patients. E-PS-06-035 Spatial transcriptome analysis and differences in immune cell infil- trate with respect to the prognostic biomarker Stroma Areactive Invasion Front Areas (SARIFA) in gastric cancer B. Grosser*, C.M. Heyer, N.G. Reitsam, D. Vlasenko, A. Probst, M. Schlesner, B. Märkl *Pathology, Medical Faculty Augsburg, University of Augsburg, Germany Background & objectives: The histomorphologic prognostic bio- marker Stroma AReactive Invasion Front Areas (SARIFA) is based on an interaction of tumour cells with adipocytes. The aim was to elucidate the changes in the tumour microenvironment, particularly the immune cell infiltrate, with respect to SARIFA-status. Methods: SARIFA was classified on H&E-stained tissue sections of a local series of gastric carcinomas and in a subset of the TCGA STAD cohort. A spatially resolved transcriptome analysis in the stroma and in macrophages at the invasion front was conducted. Apart from analyzing genomic and transcriptomic data in regard to SARIFA-status the immune cell infiltrate was analysed using Spatial Deconvolution. Results: Apart from the fact that no genomic differences were found in the TCGA STAD cohort with respect to SARIFA status, gene expres- sion analyses again revealed upregulation of FABP4 and transcriptional regulation of white adipocyte differentiation, triglyceride metabolism, and catabolism in SARIFA-positive tumours. Spatially resolved tran- scriptome analysis of SARIFA-positive tumours showed increased expression of FABP4 and transcriptional regulation of white adipocyte differentiation in macrophages. The immune cell infiltrate showed no particular distribution with respect to SARIFA groups. Conclusion: SARIFA is not driven by tumour genetics. The mecha- nisms underlying the interaction between tumour cells and fat cells need to be elucidated in further studies and could be a target for per- sonalized therapies. E-PS-06-036 Tertiary lymphoid structures before and after radiotherapy in rectal cancer (Dendritic cells – RORγt cells maintaining the immune balance) M. Gulubova*, I. Koni, I. Maria Magdalena *Dept. General and clinical pathology, Trakia University, Medical Faculty, Bulgaria Background & objectives: Conventional fractioned radiotherapy delivered in small fractions for a number of weeks, kills directly tumour cells and induced tumour cell death via anti-tumour immunity and vascular damage. RT is a double-edged sword that can activate or sup- press the immune response. Methods: We investigated 18 patients operated for rectal cancer, 5 (27.8%) before RT, and 13 (72.2%) after RT. All patients have TLS. Immunohisto- chemistry with antibodies against DC markers: CD1c, CD141, DC-SIGN, CLEC9A, CD123, CD1a and CD83; anti-lymphocyte markers: CD8, FoxP3, IL-17, and RORγT; and anti-CD163 (M1) macrophages is used. Results: After RT the main antigen-presenting cell (APC) types that are stimulated in TLS are CD1c+, DC-SIGN+, and CD83+ DCs. T lymphocyte subtypes IL-17 and FoxP3 are increased in TLS after RT. RORγT+ cells are statistically significantly increased after RT (67.28±7.04 v.s 39.11±5.27) ( χ 2=5.89, p=0.015). Conclusion: Our results show that RT stimulates recruitment of cDC2s (CD1c+), DC-SIGN+ DCs and RORγT+ cells. The latter APC fea- tures. The quantity of CD8+ T cells is not changed. Therefore, the effective immune response in TLS is not well balanced. Funding: NIP 7/22 "Tertiary lymphoid structures (TLS) - organization, localization and function in the tumour microenvironment" E-PS-06-037 Immune cell content in primary Crohn’s disease of the appendix compare to tuberculosis of the appendix M. Gulubova*, C. Dimitur, Z. Georgi, P. Mariyana, H. Mehmed, I. Koni *Dept. General and clinical pathology, Trakia University, Medical Faculty, Bulgaria Background & objectives: Tertiary lymphoid structures develop at sites of chronic inflammation, autoimmunity and cancer. TLS lack capsule and usually develop in non-lymphoid tissue. In our opinion, Crohn’s like granuloma and the tubercle itself are a kind of TLS trig- gered by autoimmune reaction. Methods: Two cases are presented: case 1: A 14 years old boy oper- ated for primary Crohn’s disease of the appendix and case 2: a 22 years old women with miliary tuberculosis of the appendix operated for appendicitis. Immunohistochemistry has been performed with anti- CD3, anti-CD20, anti-CD83, anti-CD68, anti-CD21, anti-IL-17, anti- FoxP3, anti-Bcl6, anti-D2-40, and anti-CD31. Results: In case 1 Crohn’s disease TLS are situated in the muscle layer or connective tissue of the appendix. They represent lymphoid aggregates without capsule and mainly without germinal centres. CD3+ and CD20+ lymphocytes are more loosely dispersed in TLS. CD68+ macrophages are scattered in TLS periphery, where Bcl6 cells can be found. CD83+ dendritic cells are presenting in GCs and in T zone. D2-40+ lymph ves- sels are many in the whole TLS and are full of lymphocytes. In case 2 we find subserosal tubercles show CD3+T cells in lymphocyte clusters, CD83+ DCs in the epithelioid zone, CD83+ Langhans cells. Bcl6 cells are missing. D2-40+ form a network between epithelioid cells. Conclusion: The immune content of Crohn’s granuloma is similar to Crohn’s reaction in colorectal cancer, while tubercle contains a specific immune contexture, where Langhans cells show antigen-presenting marker. Funding: NIP 7/2020 "Hepatic monocytes/Kupffer cells, NK/NKT cells, T cells, and antigen-presenting cells in the pathogenesis of non- alcoholic steatosis, non-alcoholic steatohepatitis, and tumorigenesis" E-PS-06-038 Gastric adenomyoma: a challenging diagnosis S. Gurzu*, A. Kovacs, T.J. Bara, I. Jung *George Emil Palade University of Medicine, Pharmacy, Sciences And Technology of Târgu Mureş, Romania Background & objectives: Gastric adenomyomas are rare tumours composed of ductal-like epithelial structures and smooth mus- cle fibres. Only 70 cases were reported in Medline database during