ECP 2023 Abstracts

S89 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 Somatic malignancies included carcinomas, sarcomas, neuroblastoma and high-grade glioma with squamous cell carcinoma and adenocarci- noma being the commonest entities. Conclusion: Ours is the largest study from India to study the SNs arising in teratomas. Development of somatic-type malignancies in germ cell tumours represents a significant challenge in diagnosis and treatment. They are often resistant to chemotherapy and are mostly amenable to surgical treatment. Hence, adequate sampling of teratoma with appropriate use of IHC in cases wherever deemed necessary is recommended to not miss and to correctly diagnose the associated somatic-type malignancies. PS-10-017 Phosphohistone H3 (PHH3) expression in the risk rating for endometriosis L. Lozneanu*, I.D. Căruntu, S.E. Giu ș că, R. Balan, B. Toma, R.D. Matasariu *U.M.F. "Grigore T. Popa" Iasi, Romania Background & objectives: Endometriosis represents a chronic inflam- matory disease. Phosphohistone H3 (PHH3) facilitates cellular damage and inflammation in endometriosis. As the prevalence endometriosis in Romania is high, we aim to to analyse PHH3 expression in both groups with and without Progesterone (hormonal) treatment. Methods: 30 patients with endometriosis followed up at Obstetrics and Gynaecology, Cuza Vodă Hospital, Iaşi, Romania, between 2021-2022 were retrospectively selected. Clinicopathological features and gynae- cologic examinations were assessed. Immunohistochemistry analysis for the evaluation of PHH3 expression status in endometriotic foci of both groups was performed. PHH3 was expressed in the glandular epithelium and endometrial stroma of both groups. Results: Our series included 18 (60%) cases without hormonal treat- ment and 12 (40%) cases with hormone therapy. The PHH3 negative expression was found in 16 (53%) cases, being in equal distribution in both groups, while from 14 (47%) positive expression, 10 (71%) were without hormonal treatment, and 4 (29%) with hormone therapy. Conclusion: To our knowledge, this is the first Romanian case series showing high prevalence of PHH3 in endometriosis patients with and without hormonal treatment. Positive PHH3 expression was found in the non-treatment group, showing an increasing trend compared to treatment group. PHH3 might be involved in the progression of endo- metriosis in patients without hormonal treatment. Progesterone is likely responsible for this difference. Since PHH3 showed less expression in hormone therapy group, blocking PHH3 can inhibit the progression of endometriosis. PS-10-018 "Deciduoid" change in uterine leiomyomas in pregnancy: aberrant expression of sex cord markers inhibin and calretinin J. Machuca Aguado*, G. McCluggage *Virgen Macarena University Hospital, Seville, Spain Background & objectives: Leiomyomas are common hormone respon- sive uterine neoplasms which can exhibit a variety of morphological changes secondary to hormonal agents such as progestogens. Surpris- ingly the morphological features of leiomyomas in pregnancy are not well described in the literature. Methods: Retrospective observational clinicopathological study of a series of 29uterine leiomyomas inpregnancy. Clinicopathological featureswere collated. Results: The morphological features included, in decreasing order of frequency, infarct-type necrosis, decidualisation of the serosal surface, hyalinisation, myxoid alteration of the stroma, oedema (sometimes with cyst formation) and dystrophic calcification. We also report a feature which we term “deciduoid” change (seen in 10 of 29 leiomyomas) which takes the form of altered smooth muscle cells with an epithelioid morphology with abundant eosinophilic or clear cytoplasm. Further- more, we show that the “deciduoid” cells commonly exhibit expression of sex cord markers inhibin and calretinin. We speculate on the patho- genesis of the “deciduoid” change which together with its “aberrant” immunophenotype may result in diagnostic problems and consideration of other neoplasms. Conclusion: We report the histological features in a series of leio- myomas in pregnancy. These include an alteration which we term “deciduoid” change because of the resemblance to decidualised stromal cells. We believe these “deciduoid” cells represent modified smooth muscle cells probably altered by the hormonal milieu of preg- nancy. These “deciduoid” cells can exhibit an unusual immunopheno- type, including aberrant expression of inhibin and calretinin; the mor- phological alterations and aberrant immunophenotype may result in diagnostic problems if pathologists are unaware of this phenomenon. PS-10-019 Tumour-infiltrating lymphocytes (TILs) digital quantification as a relevant prognostic biomarker in high-grade serous ovarian cancer J. Machuca Aguado*, A.F. Conde-Martín, A. Álvarez-Muñoz, E. Rodríguez-Zarco, J.J. Rios Martin, M.A. Idoate Gastearena *Virgen Macarena University Hospital, Seville, Spain Background & objectives: It is postulated that Tumour Infil- trating Lymphocytes (TILs) can have a significant prognos- tic and predictive role in high-grade serous ovarian carcinoma (HGSOC). However, only three studies have reported the prog- nostic value of TILs in HE-stained sections in this tumour type. Methods: 76 molecularly and clinically, well characterized HGSOC III/IV staged (FIGO) cases were studied. HE-stained sections were evaluated digitally using learning image analysis algorithms. IeTILs (ratio intrachordonal immune cells number/tumour cells number) and sTILs (immune cells number in the stroma/total stromal area) were quantified and correlated with disease free survival (DFS) and overall survival (OS). Results: Interestingly, 40% of cases showed intense colonisation of tumour chords by TILs, especially in cases which had received neo- adjuvant treatment. A correlation between DFS with ieTILs (r=0.252; p=0.028) and sTILs (r=0.231; p=0.045) was observed. Furthermore, this correlation showed greater significance when tumours were assessed by median, with high-ieTILs showing longer DFS than low-ieTILs (median 33 months vs. 20 months; p=0.008). The same was found for high-sTILs when compared to low-sTILs (median 31 months vs. 18 months; p=0.033). In addition, high-ieTILs demonstrated a longer five-year survival when compared to low-ieTILs (77% versus 29.9%; p=0.028). However, this was not observed in sTILs. Conclusion: We consider that the quantification of TILs on H&E-stained sections using a digital quantification is an appropriate approach for clini- cal purposes. We have shown that quantification of TILs, especially TILs location, could be a relevant prognostic parameter in HGSOC, supporting the role of antitumour effect of immune response in ovarian cancer. PS-10-020 Molecular classification of endometrial carcinoma (EC): a single institution experience with 144 ECs exclusively tested by NGS K. Michalova*, O. Ondic, J. Presl, P. Martinek, N. Hejhalova, A. Hluchy, A. Strakova-Peterikova, M. Michal, M. Michal *Department of Pathology, Faculty of Medicine in Pilsen, Charles Uni- versity, Pilsen, Czech Republic Background & objectives: POLEmut ECs have excellent prog- nosis requiring no adjuvant therapy. Sanger sequencing is used for