ECP 2023 Abstracts

S76 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 with high risk for ESRD can be identified by quantification of macrophages in native renal biopsies. Further studies will show whether macrophages have a bystander or independent role in renal injury. Macrophages might be a promising therapeutic target in different renal diseases. JS and JHB received funding from German Federal Ministry of Educa- tion and Research (BMBF No. 13GW0399B). PS-07 | Poster Session Other Topics PS-07-001 HPV infection is linked to enriched T- and dendritic cell infiltration in squamous cell carcinomas from 8 different origins N. Blessin*, N.F. Debatin, E. Bady, J.H. Müller, T. Mandelkow, R. Simon, M. Lennartz, G. Sauter, E. Burandt, S. Steurer, T.S. Clauditz, C. Bernreuther, A. Menz *Institute of Pathology, University Medical Center Hamburg-Eppendorf, Germany Background & objectives: Given that HPV infection is gener- ally accompanied by gene alterations, epigenetic changes, and altered microRNA expression in squamous cell carcinomas (SCCs), the composition and degree of immune checkpoint expres- sion on immune cell subtypes might be linked to the HPV status. Methods: To study differences between 199 (51%) HPV-associated and 194 (49%) HPV-independent squamous cell carcinomas from 8 different origins, the spatial interplay of more than 30 TIM3, CTLA- 4, PD-1/-L1 expressing leukocyte subpopulations was analysed in a tissue microarray format using our 21-marker-BLEACH&STAIN multiplex fluorescence immunohistochemistry approach and ana- lysed using a deep learning-based image analysis framework. Results: The density of CD8+ cytotoxic T-cells, CD4+ T-helper cells, and CD11c+ dendritic cells, irrespective of the tissue compartment, was significantly linked to HPV-positivity (p≤0.006 each), while the density of FOXP3+ T-cell, CD20+ B-cells, M1/ M2 macrophages showed no difference between HPV positive and negative cases. Inter- estingly, except for reduced CTLA-4 expression on CD4+ T-cells in HPV positive cases, no other link between immune checkpoint expression and HPV status was found. A significantly higher inter- action pattern between CD8+/ CD4+ T-cell and CD11c+ dendritic cells (p<0.001) as well as between CD8+ cytotoxic T-cells and CD4+ T-helper cells (p=0.005) was found in HPV-associated SCCs. Conclusion: HPV-associated squamous cell carcinomas of various origins were characterized by a higher degree of cytotoxic and helper T-cell as well as dendritic cell density and a reduced CTLA-4 expres- sion on T-helper cells compared to HPV independent cases. In addi- tion, a stronger interaction network between non-regulatory T-cells and dendritic cells was linked to HPV-associated SCCs. PS-07-002 An evaluation of physician’s knowledge and practices about pre-ana- lytical phase in pathology: the first survey-based study in Morocco S. Chaib*, J. Kharmoum, M. El jiar, I. Eliahiai, M. Chraibi *University Hospital Mohammed VI, Morocco Background & objectives: The pre-analytical phase in pathology is crucial in obtaining reliable analysis results. Mismanagement of this phase can compromise the quality of results, which may impact clinical decisions and patient treatments. Methods: We conducted a national cross-sectional anonymous sur- vey among Moroccan physicians regarding the pre-analytical phase in pathology, designed on the Google Forms platform. The target popu- lation is physicians practicing in the public, academic, and private sectors, responded to questionnaire covering various aspects of the pre-analytical phase. A total of 341 participants were surveyed includ- ing 52,4% resident, 22,7% interns, and 4,5% professors. Results: Results found 94,5% of participating physicians didn’t receive any training on the pre-analytical phase. Specific knowledge was also limited, with a percentage of ignorance regarding the fixative (20.3%), and the required volume to fix samples (80%). 13.7% don’t routinely orient their specimens, while 16.2% always open specimens. 15% believe that not all tissue samples need to be sent for histologi- cal examination. 47.4% think that it is acceptable to store specimens without fixative in a refrigerator for more 24H. We noticed that inad- equate practices in case of fixative unavailability; using plastic bags (38.2%). Poor contact with pathologists were reported (95.1%). 80,7% were unaware of the effect of fixation on anatomopathological study. Conclusion: This study revealed significant gaps in the management of specimens. Solutions such as practical workshops, practical guides posters in departments, and a platform to facilitate communication between physicians and pathologists have been proposed to address these gaps and ensure quality healthcare. PS-07-003 Using propidium iodide instead of DAPI can expand the use of stored tissue samples for immunofluorescence K. Cizkova*, K. Koubova, Z. Tauber *Department of Histology and Embryology, Faculty of Medicine and Dentistry, Palacky University, Olomouc, Czech Republic Background & objectives: Archival tissues are a rich source of potential material for retrospective and comparative studies. Clear detection of nuclei is crucial in immunofluorescence however we observed blurred, poor quality DAPI staining of nuclei in several archival specimens. Methods: We investigated the effect of aging of tissue blocks on the quality of nuclear staining. Placental tissue samples stored for 1, 5, 18 and 26 years were examined for DAPI and propidium iodide staining. ImageJ software was used to detect nuclei. In addition, the same samples were stained with haematoxylin to confirm tissue integrity. Results: Although haematoxylin staining showed good quality in all sam- ples, DAPI staining deteriorated with increasing age of the tissue blocks, a phenomenon that could be improved by using propidium iodide. Replac- ing DAPI with propidium iodide significantly increased the detectability of nuclei in tissue blocks stored for 18 or 26 years using ImageJ software. Conclusion: Based on our results, we suggest that replacing DAPI with propidium iodide could extend the use of immunofluorescence tech- niques to archival tissue samples. PS-07-004 Comparison of INSM1 immunostaining with established neuroen- docrine markers Synaptophysin and Chromogranin A in over 14,000 neuroendocrine and non-neuroendocrine tumours K. Möller*, N. Gorbokon, D. Dum, C. Hube-Magg, C. Fraune, M. Lennartz, N. Blessin, E. Burandt, R. Krech, T. Krech, A.H. Marx, G. Sauter, R. Simon, C. Bernreuther, S. Minner *Institute of Pathology, University Medical Center Hamburg-Eppen- dorf, Germany Background & objectives: INSM1 is a transcription factor protein which is increasingly used as an immunohistochemical marker for neu- roendocrine differentiation. Methods: To determine the prevalence of INSM1 expression in tumours and its expression pattern in normal tissues, tissue micro- arrays containing 14,908 samples from 117 different tumour types/ subtypes as well as 76 different normal tissues were analysed by immunohistochemistry. Results: INSM1 was positive in 89.2% of 471 neuroendocrine neo- plasms (NEN) and in 3.5% of 11,815 non-neuroendocrine neoplasms