ECP 2023 Abstracts

S255 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 Conclusion: Widespread intraperitoneal and visceral deposition of ORS reminants, a hemostatic agent applied intraoperatively, posed a histopatho- logical challenge in the present case, due to its mucin-like appearance. We presented this case to raise awareness of pathologists on this issue. Surgeons and radiologists should also be aware of this complication related to the use of ORS, as cases have been reported in the literature, presenting with an abdominal/pelvic mass or with an acute clinical condition. E-PS-10-013 Incidence and evolution of carcinosarcomas in 10 years in a pro- vincial hospital T. Cano*, E.M. Ariza, B. Garzón, J.J. Sánchez, M.C. González, G.A. Pastrana *Juan Ramón Jiménez University Hospital, Huelva, Spain Background & objectives: Uterine carcinosarcoma is an aggressive biphasic high-grade tumour with a carcinomatous and sarcomatoid component. It is a rare tumour accounting for 5% of uterine malignan- cies. It usually occurs in elderly women. The pathological study playing a fundamental role. Methods: The cases obtained in the last 10 years in our hospital are reviewed, obtaining diagnostic concordance data in aspiration biopsy and surgical piece, age of presentation, stage and type of sarcomatoid component (classifying it as homologous, if the sarcomatous element is native to uterine tissue, or heterologous, if the sarcoma is not native). Results: N=11, age range from 59 to 84 years, presenting in all of them endometrioid carcinoma in its carcinomatous component and heterologous component in 7 of them (1 with osteosarcoma differen- tiation, 3 rhabdomyosarcomatoid , and 3 chondrosarcomatioids) in the mesenchymal component. At the macroscopic level, most were a fleshy polypoid mass with necrotic and haemorrhagic areas. 2 of the 11 cases presented metastasis at the initial diagnosis, 1 pre- sented parametrial invasion (pT3b), 7 presented myometrial invasion >50% (pT1b) and in 1 it was <50% (pT1a). In only 2 of the 3, there was no good diagnostic correlation in aspira- tion biopsy, initially being diagnosed as endometrioid carcinoma, with no evidence of sarcomatoid. Conclusion: In summary, carcinosarcoma is a rare and aggressive tumour of the uterine body, in which the pathologist plays a crucial role for diagnosis, although the correlation in aspiration biopsy and surgical specimens is not complete, early diagnosis is still necessary to improve the patient survival. The prognosis is usually poor, in 30-40% of cases there is extrauterine involvement in the initial presentation, but in our population only 2% presented metastases at diagnosis. E-PS-10-014 Mesonephric-like adenocarcinoma of endometrium: a wolf in sheep’s clothing T. Čeprnja*, I. Jurković, D.A. Grubišić, S. Tomić *University Hospital of Split, Croatia Background & objectives: Mesonephric-like adenocarcinoma of endometrium is a recently described rare entity sharing histological, immunohistochemical and molecular characteristics of mesonephric carcinomas, but lack association with mesonephric remnants or char- acteristic location. We present a case of this very rare subtype of endo- metrial adenocarcinoma. Methods: Postmenopausal 55-year-old female presented with abnor- mal uterine bleeding and lower-back pain. On curretage diagnosis of serous adenocarcinoma was made, and total hysterectomy with bilateral salpingo-oophorectomy, pelvic lymphadenectomy and omentectomy was performed and a final diagnosis of endometrial adenocarcinoma with clear-cell differentiation, with unusual immunophenotype was set. Another opinion was requested, and materials were sent to our department. Results: Histology showed a uterine carcinoma composed of round, compacted glands focally with eosinophilic material. Rare reticular and papillary structures lined by atypical cells with vesicular nuclei and solid area composed of spindled cells were also observed. Immunohistochemi- cally, tumour cells were TTF-1, CD10 (luminal staining) and e-cadherin positive and had wild-type p53 immunoexpression. Few tumour cells were napsin positive, and p16ink was intensively positive in small part of the tumour. ER, PgR, AMACR, GATA3 and calretinin stains were nega- tive. Additional molecular analysis showed KRAS and PIK3CAmutation. Conclusion: Mesonephric-like adenocarcinoma of the endometrium is a recently described rare subtype of endometrial adenocarcinoma. Ability to mimic more common subtypes makes it a challenging diag- nosis for gynaecologic pathologists. Although data is limited for now, it seems that mesonephric-like adenocarcinomas are high-grade carci- nomas, even though they have a misleadingly low-grade morphology. The tumours have a high risk of recurrence and a high tendency for metastasis. E-PS-10-015 Ovarian yolk sac tumour in the background of serous carcinoma – a report of a rare entity A. Chrzan*, M. Bidziński, J. Kupryjańczyk *Maria Sklodowska-Curie National Research Institute of Oncology (MSCNRIO), Department of Cancer Pathomorphology, Warsaw, Poland Background & objectives: Yolk sac tumours (YST) may sometimes develop from somatic malignancies, predominantly endometrioid tumours. Herein, we report a rare case of YST arising from high grade ovarian serous carcinoma (HGSC) in a postmenopausal woman. Methods: A 72-year-old female was referred to our hospital for the pel- vic mass and slightly elevated serum CA125, HE4 and LDH. A trans- vaginal ultrasound revealed a 45 mm solid tumour of the left ovary. The patient underwent total hysterectomy with bilateral salpingo-oopho- rectomy and staging surgery. Frozen section evaluation resulted in the misdiagnosis of endometrioid carcinoma (EC). Results: Microscopic examination revealed co-existing endometrioid- like glandular YST resembling secretory EC, solid areas with ambigu- ous morphology, and HGSC, which comprised 80%, 15% and 5% of the tumour, respectively. Immunohistochemically, the YST component was positive for SALL4, AFP, Glypican-3, and focally for GATA3, whereas negative for PAX8, CK7, WT1, and Napsin A. The HGSC component was positive for PAX8, WT1 and negative for YST markers. Solid areas exhibited an intermediate immunoprofile. All components showed EMA positivity and mutation-type p53 staining. Mutations in BRCA1/BRCA2 genes were not found. The serum AFP measured post- operatively was elevated (225.90 IU/ml). Therefore, a final diagnosis of ovarian YST derived from HGSC was rendered (FIGO stage IC3). Conclusion: It is postulated that YST can arise from a carcinoma through a process of retrodifferentiation. Somatically derived YST may retain EMA expression. The presence of TP53 accumulation in both components confirms their clonal relationship. Possibly, areas with the intermediate immunoprofile reflect a transient stage from carcinoma to YST. The preexisting neoplasm can be totally or nearly totally over- grown by YST therefore thorough sampling is essential. E-PS-10-016 SMARCB1-deficient myoepithelial carcinoma of the vulva in a pregnant woman: a rare and aggressive tumour Y. Chun*, J.Y. Park, Y. Kim *Korea University Guro Hospital, Republic of Korea Background & objectives: Myoepithelioma-like tumours of the vulva are rare mesenchymal tumours that are associated with SMARCB1 loss. Vulvar myoepithelial carcinoma is even rarer. We report a case of