ECP 2023 Abstracts

S90 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 POLEmut detection but in comparison with NGS has 50% sen- sitivity, leading to overtreatment of POLEmut patients. We share our experience with molecular classification performed by NGS. Methods: All molecularly classified EC from Pilsen Faculty hospital were included. All cases were examined by morphology, IHC (MSH2, MSH6, PMS2, MLH1, p53) and by NGS with GynCore oncopanel (Archer, Inc) specifically designed for EC and containing 16 genes of interest. Clinical data were obtained from the electronic database of the hospital. Results: The cohort included 144 patients and was composed of 7 POLEmut EC (4.99%; 3 endometroid EC grade 3, 4 endometroid EC (grades 1-2)), 41 MMRd EC (28.5%; 31 sporadic EC, 10 suspi- cious of Lynch syndrome), 80 NSPM EC (55,6%) and 16 TP53mut EC (11,1%). The mean follow-up time was 45 months. Ninety-seven patients were alive, with no signs of recurrence, including 5/7 POLEmut EC, 26/41 MMRd EC, 63/80 NSMP and 3/16 TP53mut. The remain- ing 2 POLEmut patients are alive with disease, both were diagnosed at stage 3 (FIGO IIIA and IIIC1, respectively), the time of follow-up was 28 and 30 months, and patients aged 59 and 88 years, respectively. Conclusion: Our large cohort encompassing 144 prospectively studied EC classified exclusively by NGS into 4 molecular groups further high- lights the importance of incorporation of routine molecular classification of EC as it has a high impact on patient´s management. Furthermore, the importance of using NGS for detection of POLE mutations needs to be emphasized as this method is far more reliable than Sanger sequencing. PS-10-021 Tumour infiltrating lymphocytes in early-stage high grade serous ovarian cancer: prognosis significance of visual and digital analysis S.MolésCaparrós*, A. VelizDominguez, J.C. Corredor-García, A. Tenelanda- Santillán, N. Cadavid-Fernández, I. Romero, J.A. López-Guerrero, A. Poveda, I. Carretero-Barrio, B. Pérez-Mies, J. Palacios Calvo *Ramón y Cajal University Hospital, Spain Background & objectives: The aim of this study is to determine the prognosis significance of CD4 and CD8 tumour infiltrating lym- phocytes (TILs) in early-stage high grade serous ovarian carcinoma (HGSOC) and determine whether digital quantification can improve prognosis stratification in those patients. Methods: We studied TILs in HGSOC tissue microarrays cores stained with CD4 and CD8. We counted intraepithelial and stromal TILs visu- ally and with digital analysis, establishing >20 TILs/core as high TILs. We used QuPath to perform the digital analysis. We studied the correla- tion between visual and digital count and performed a survival analysis comparing tumours with high and low TILs. Results: We evaluated 109 patients: 51 for intraepithelial (i) and stro- mal (s) CD4 and CD8 TILs, 29 for CD4, and another 29 for CD8. We found statistically significant differences in mean TILs between visual and digital analysis in all settings (iCD4, iCD8, sCD4, SCD8 TILs). For example, visually the average iCD8 count was of 25.5 TILs/core, whereas digitally it reached 46.5. We also found a positive linear cor- relation between visual and digital count. With both visual and digital analysis, high iCD8 TILs were associated with better survival. How- ever, only with visual analysis we found better survival in patients with low iCD4 TILs. Conclusion: There is an association between TILs and prognosis in early stages of HGOC: higher iCD8 TILs, as well as lower iCD4 TILs, entail better outcomes. Digital analysis showed a good correlation with visual analysis, proving its value as an assistant diagnostic tool. How- ever, more studies should be done in order to improve its usefulness for prognosis stratification in HGSOC. This research was supported by CIBERONC (CB16/12/00316), Insti- tuto de Salud Carlos III, Ministerio de Ciencia e Innovación and Unión Europea – European Regional Development Fund. This study has been funded by Instituto de Salud Carlos III (ISCIII) through the project “PI22/01892” and co-funded by the European Union. Developed with the financial support of Immune4ALL Project (PMP22/00054), with European funds of the Recovery, Transformation and Resilence Plan, and financed by the Instituto de Salud Carlos IIII. Supported by the Spanish Group of Research in Ovarian Cancer (GEICO group). PS-10-022 Clinicopathological and molecular features of mesonephric-like adenocarcinoma of uterine corpus C. Mora*, J. Ferreira, F. Cunha, F. Silva, P. Silva, C. Albuquerque, A. Félix *Serviço de Anatomia Patológica, Instituto Português de Oncologia de Lisboa Francisco Gentil, Lisbon, Portugal Background & objectives: Mesonephric-like adenocarcinomas (MLA) are rare tumours of the uterine corpus with a poor prognosis. Differential diagnosis can be difficult. Frequent KRAS mutations have been described. We report the clinicopathological and molecular findings in a series of MLA. Methods: Five MLA cases were included. Clinical data was retrieved. H&E and immunohistochemistry (GATA3,TTF1,CCD10,p53,ER,PR) slides were reviewed. NGS targeting KRAS, NRAS, PIK3CA, PTEN, POLE, TP53, EGFR, BAP1 and CTNNB1 mutations was performed. Results: Patients’ median age was 72 years old(48-75yrs). FIGO stage distribution was IA(1),IB(1),II(2),IVB(1). Patients were treated with surgery(n=5) and adjuvant chemo/radiotherapy(n=4). All neoplasms showed a variety of histological patterns. Numerous LVI were observed in 4 cases. Tumours were GATA3+(5/5), TTF1+(4/5), CD10+ api- cal staining(4/5), p53 wild-type(4/5), ER/PR negative(5/5). In one tumour, p53 null pattern was observed. Inverted GATA3/TTF1 stain- ing was observed in 3 cases. All tumours were MMR proficient(3/3). Four cases harboured pathogenic KRAS mutations, three with c.35G>T p.(Gly12Val), and one with c.35G>C p.(Gly12Ala). No mutations were found in the other genes analysed. During a median follow-up of 21 months (11-46), three patients developed recurrence/distant metastasis, and two died of the disease. Conclusion: In our series, all but one case had at least 2 mesonephric markers expression. One case only had GATA3 expression but had typical morphology and was KRAS mutated. KRAS mutations are a frequent event. p53 mutated pattern was observed in one case with oth- erwise typical morphology and immunohistochemical findings, which can aggravate diagnostic challenge. Irrespective of stage, MLA is a highly aggressive neoplasm. PS-10-023 Endocervical adenocarcinoma (ECA): Reclassification as per IECC into HPV associated(HPVA) and HPV independent(HPVI) using morphology, P16INK4a immunohistochemistry and HR-HPV RNA in situ hybridization(ISH) A. Mundada, K. Deodhar*, B. Rekhi, S. Menon, N. Mittal, O. Shetty, O. Salvi *Tata Memorial Hospital, Homi Bhabha National University, India Background & objectives: The year 2018 witnessed a breakthrough in the field of cervical adenocarcinoma when Stolnicu and colleagues proposed a new pathogenetic classification for endocervical adenocarcinomas based on their associationwithHPVwhichwas adopted by theWHO in the 2020 update. Methods: Retrospective study was undertaken at a tertiary care oncol- ogy centre in India to study the clinical and pathological features of cases of ECA whose resection specimens were received at the depart- ment of pathology from 2016 to 2020. Cases were classified as HPVA or HPVI based on morphology by two pathologists and compared with results of immunohistochemistry for p16INK4a and HR-HPVISH. Results: The IECC morphologic classification had perfect interob- server agreement in 76/79 (96.2%) cases. HPVA cases n=68 (86%) with usual 77.9%, mucinous 10.2%, intestinal 4.4%, ISMC 4.4% and