ECP 2023 Abstracts

S256 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 SMARCB1-deficient myoepithelial carcinoma of the vulva in a preg- nant woman. Methods: A 30-year-old pregnant woman presented with a vulvar mass that had been present before her pregnancy and had increased in size. The mass measured 8 x 7cm. Complete resection was performed, followed by radiation treatment. Twelve months later, the patient developed multiple lung metastases. Chemotherapy with paclitaxel and cisplatin was adminis- tered, but multiple pleural and paraaortic soft tissue metastases developed. Results: Pathological examination of the vulvar tumour revealed a multinodular mass with an infiltrating margin. The tumour consisted of epithelioid to spindle cells growing in a reticular pattern, with myxoid or hyalinized stroma. Mitotic figures were 5 per 10 high-power fields. Immunohistochemical staining showed expression of EMA, SMA, and calponin, and loss of INI-1. ER and PR showed diffuse and focal positivity. Next-generation sequencing revealed the possibility of a heterozygous deletion of the SMARCB1 gene. Conclusion: We report a case of SMARCB1-deficient myoepithe- lial carcinoma of the vulva in a pregnant woman, which exhibited an aggressive clinical course despite surgical and post-operation chemo- radiation treatments. As ER and PR were positive, it is possible that the tumour grew rapidly due to pregnancy. It is challenging to differentiate between myoepithelioma-like tumours of the vulva and myoepithelial carcinomas as both tumours are SMARCB1/INI1-deficient and exhibit similar histological features. Therefore, a collective review is needed to unify the diagnostic criteria. E-PS-10-017 Expression of Osteopontin in serous ovarian carcinoma R. Chyzhma*, R. Moskalenko *Sumy State University, Ukraine Background & objectives: Ovarian cancer is one of the most common causes of death among women worldwide. One of the clinical and mor- phological features of ovarian tumours is calcification. To study the OPN expression in serous ovarian carcinoma with and without calcification. Methods: We examined 30 samples of serous ovarian carcinoma with calcification and 30 samples of serous ovarian carcinoma without cal- cification. An immunohistochemical study was performed using an Anti-Osteopontin antibody (OPN, ab 8448, Abcam, Cambridge, Great Britain) with dilution 1:300. Results: An immunohistochemical study of ovarian carcinoma showed the accumulation of OPN in biominerals. Protein covers the surface of the calcification, accumulating at the edges and between the lamellae. A positive cytoplasmic reaction to OPN is observed in the microenviron- ment cells, mainly mononuclear morphology and fibroblast-like cells. The difference between the results of an immunohistochemical study of OPN expression in groups of serous ovarian carcinoma samples with (73.34 ± 4.25 cells per 1mm2) and without calcification (26.93 ± 1.88 cells per 1mm2, p<0.001). This may indicate the participation of OPN in the pathological biomineralization of serous ovarian carcinoma. Conclusion: Therefore, pathological biomineralization leads to high levels of OPN protein expression in serous ovarian carcinoma. On the other hand, samples of serous carcinoma without calcification have a lower level of these proteins. E-PS-10-018 Development of a CD138-based histopathological semiquantitative scoring system for the diagnosis of chronic endometritis: inter- observer agreement between trained pathologists and a newly designed QuPath computational algorithm S. De Smet*, G. Tagmouti, R. Forsyth, W. Waelput *Universitair Ziekenhuis Brussel (UZB), Belgium Background & objectives: It is accepted that the presence of plasma cells in the stromal endometrium is a marker for chronic endometritis. This study’s objective was to develop a histopathological semiquantita- tive scoring system for its diagnosis, as well as assessing inter-observer agreement. Methods: In a retrospective analysis of endometrial biopsies from 75 patients with suspected chronic endometritis, six pathologists scored the degree of inflammation using our proposed CD138-based semi- quantitative scoring system. In addition, a newly developed QuPath computational algorithm was considered a seventh observer. A con- sensus score was determined after reviewing all cases. Inter-observer agreement was calculated using weighted kappa statistics. Results: The CD138-based semiquantitative scoring system showed particularly good to excellent inter-observer agreement between all observers, including the computational algorithm. Weighted kappa values were ranging from 0.81 to 0.96 (p<0.001) in a four-tier system, and from 0.72 to 0.97 (p<0.001) in a two-tier system. Conclusion: We have developed a histopathological semiquantitative scoring system for the diagnosis of chronic endometritis, with particu- larly good to excellent inter-observer agreement among pathologists. This scoring system has the potential to become a new standardized tool to classify the severity of inflammation in chronic endometritis. It provides an excellent tool for further studying the diagnosis of chronic endometritis, and its correlation with clinical outcomes. In addition, our computational algorithm could deliver enhanced accuracy and effi- ciency in the diagnosis of chronic endometritis. E-PS-10-019 Small cell carcinoma of the ovary, hypercalcemic type (SCCOHT) in a 50 year old woman. Case report and literature review M. De Uribe Viloria*, G. Barrios Millán, A. Berjón *La Paz University Hospital, Spain Background & objectives: SCCOHT is a rare and aggressive tumour mainly affecting premenopausal women. Patients usually present with advanced-stage disease. The median survival time is around nine months. Inactivating SMARCA4 mutations are thought to be the main driving molecular event. Methods: We reviewed our files from 2013 to April 2023 retrieving a single case of SCCOHT. The diagnosis was achieved by routine stain- ings and immunohistochemical studies. We reviewed the histological samples and obtained clinical data such as age at diagnosis, symptoma- tology and radiological studies, from the clinical history. Results: We present the case of a 50 year old female who consulted with abdominal pain. The patient showed hypercalcemia and peritoneal carci- nomatosis in the CT scan. A diaphragmatic mass was biopsied showing a tumour displaying sheet-like growth, conformed by monotonous dis- cohesive round cells with scant cytoplasm, small hyperchromatic nuclei, irregular chromatin and a brisk mitotic activity. Necrosis was present. The immunohistochemical expression of BAP1 and INI1 was preserved while it the expression of BRG1 (SMARCA4) was lost. Other immuno- histochemical determinations were no specific. A diagnosis of SCCOHT was emitted. The patient died less than two months after diagnosis. Conclusion: SCCOHT is a rare tumour, accounting for less than 1% of ovarian tumours. It poses a diagnostic and management challenge. Our case presents typical pathological and clinical findings, in spite of occurring at an older age than these tumours usually present. This case report emphasizes the importance of performing BRG1 staining on undifferentiated ovarian tumours, even if the epidemiological presenta- tion is not typical. More studies are needed to address the challenges of this rare and deadly disease. E-PS-10-020 Cotyledonoid dissecting leiomyoma (Sternberg tumour) - a rare and peculiar tumour A. Dumitru*, M. Sajin, O. Munteanu, O.C. Voinea, A. Ciongariu, D. Tapoi, M. Cirstoiu