ECP 2023 Abstracts

S389 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 Methods: Prospective study, in which ten histological slides were exposed in OM for 21students and in VM for 24students.Thechoice of learning method was made by draw. An evaluation of the acquisition of knowledge was carried-out using multiple-choice questions. An assess- ment of the degree of satisfaction with the learning method used was based on a questionnaire. Mann-Whitney nonparametric-test was thus used to compare the means between groups. Results: Regarding the acquisition of knowledge, the scores varied from 8 to 15, with a median of 13/15, for each of the 2 groups. There was no significant difference between the means obtained for each group (respectively 12.67 +/- 0.48 for the OM and 12.75 +/- 0.391 for the MV, p = 0.935). Regarding the degree of satisfaction, a statistically significant difference was noted between the 2 groups for each of the 6 items tested. The overall convenience score was significantly better for the VM (p = 0.001), whereas for the overall IM score there was no significant difference between the 2 groups (p = 0.297). Conclusion: The performance of the VM is comparable to that of the OM. Taking into consideration its best convenience, VM could serve as an alternative tool to OM in teaching general pathology to students, although it does not fully satisfy their IM. E-PS-25-005 Revolution in pathology, no more formalin fixation! M. Hoogland*, A.M. Eshuis, P. van Smeerdijk, J. van der Starre- Gaal *Isala, The Netherlands Background & objectives: Formaldehyde is banned, except in medical sector. In 2012 supercritical CO2 in tissue processing was discovered. Validation was performed on formalin-fixed tissues. We examined morphology and some of the most widely used markers on tissues, freshly processed in supercritical CO2. Methods: Fresh human tissues were collected and split. One sample pro- cessed using conventional methods (FFPE, Formalin Fixed Paraffin Embed- ded). The second sample freshly processed in non-toxic supercritical CO2 (NFPE, Non Fixed Paraffin Embedded). HE staining was performed and a tissue library was built. Ten widely used histochemical and ten immunohis- tochemical markers were selected to validate on NFPE tissues. Results: Six histological markers (Elastica von Giesson, Giemsa, Mas- son Goldner, PAS, PAS-diastase and Schmorl) needed no adaptations to the standard protocol. Three histological markers (Alcian blue, Azan and Hale’s iron) needed small changes to the standard protocol. One histological marker, reticulin, needs a formalin dip to result in a near perfect staining pattern. Five immunohistochemical markers (cytokeratin AE1/AE3, CDX2, e-cadherin, CD20 and SOX10) needed no adaptations the standard protocol. For three immunohistochemical markers (TTF1, P63, CD3), small changes to the standard protocol were needed. For two markers, (CD68 and PAX-8) all adaptations did result in a more or less usable but not completely specific staining pattern, however not always specific. Conclusion: Diagnostic tissue processing without formalin is possi- ble, reliable and safe with the use of supercritical CO2. A future with hardly any, or no formaline at all. Nine out of ten tested histochemical markers and eight out of ten immunohistochemical markers perform near perfect on formalin free, processed tissues. One marker, Reticulin, still needs a small amount of formalin in the process to perform well. Two immunohistochemical markers were less perfect, application of another antibody, other epitope might solve this. E-PS-25-006 Revolution in pathology, no more formalin fixation! Supercritical CO2 tissue processing for immunofluorescence with improved morphology M. Hoogland*, J. van der Starre- Gaal, N. van der Horst *Isala, The Netherlands Background & objectives: Formaldehyde is banned, except in medical sector. In 2012 supercritical CO2 in tissue processing was discovered. Validation was performed on formalin-fixed tissues. We examined morphology and specificity of immunofluorescence (IF) on tissues, freshly processed in supercritical CO2. Methods: Appropriate fresh human tissues were collected and split. One sample processed using conventional freezing method (frozen section). The second sample freshly processed in TISPA II tissue processor (NFPE, Non Fixed Paraffin Embedded). HE staining was performed and a tissue library was built. Conventional IF (IgA, IgG, IgM, C3c, C1q, kappa and lambda) were validated on the NFPE tissues. Results: Several tissues were collected known for their autofluores- cence properties for one or more of the tested markers, as well as tonsil tissue, widely used as positive control. In the HE slides, morphology was markedly superior in the NFPE tis- sues compared to the frozen slides. IgA, IgG, IgM, kappa, lambda, C3c and C1q all performed as expected, on the NFPE tissues, with minor changes to the conventional protocol (Ventana Benchmark Ultra). Background staining in kappa and lambda improved with a prolonged washing in physiological salt after deparaffination. Conclusion: Immunofluoresence is usually performed on frozen tissues (used in primary kidney disease and bullous skin disease diagnostics), with a highly specific staining pattern, but with loss of morphology due to freezing artifacts. In the NFPE tissues, both morphology and a highly specific staining pattern are combined. Diagnostic tissue processing without formalin is possible, reliable and safe with the use of supercritical CO2. A future with hardly any, or no formalin at all. E-PS-25-007 Carcinoembryonic antigen (CEA) expression in human tumours: a tissue microarray study on 15,413 tumours K. Jansen*, L. Kornfeld, M. Lennartz, N. Blessin, S. Dwertmann Rico, S. Kind, V. Reiswich, A.M. Luebke, C. Hube-Magg, F. Büs- check, A. Menz, R. Uhlig, G. Sauter, R. Simon, C. Bernreuther *Department of General, Visceral and Thoracic Surgery, University Medical Center Hamburg-Eppendorf, Germany Background & objectives: Carcinoembryonic antigen (CEA; CEACAM5) is a cell surface glycoprotein which constitutes an attrac- tive therapeutic target and serum CEA is used for cancer monitoring. CEA is overexpressed in various cancers, but the reported prevalence data vary considerably for many tumour types. Methods: To comprehensively determine CEA expression in normal and neoplastic tissues, a tissue microarray containing 15,413 samples from 120 different tumour types and subtypes as well as 76 different normal tissue types were analysed by immunohistochemistry. Results: CEA positivity occurred in 65 of 120 tumour categories including 49 entities with at least one strongly positive case. CEA positivity was most common in colorectal carcinomas (98.7%), other gastrointestinal adenocarcinomas (61.1%-80.3%), medullary carci- nomas of the thyroid (96.3%), pulmonary adenocarcinoma (73.7%), mucinous carcinomas of the ovary (79.8%) and the breast (43.2%), squamous cell carcinomas of various sites (30.2%-69.1%), and small cell carcinomas of the lung (64.3%), the urinary bladder (38.9%), and the prostate (50.0%). High CEA expression was linked to high grade (p<0.0001) and invasive growth (p<0.0001) in urothelial carcinoma. Reduced CEA expression was associated with mismatch repair defi- ciency (p<0.0001) but not with pT and pN stage in colorectal cancer. Conclusion: In summary, CEA is abundantly expressed in a broad range of epithelial neoplasms. Our data thus identify various tumour entities where CEA positive cancers might best benefit from CEA serum monitoring and anti-CEA therapies.