ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 Conclusion: NECC is characterized by high incidence of lympho- vascular invasion and distal metastasis. Women with NECC have a poor prognosis irrespectively of the treatments used. E-PS-09-016 Endometrial carcinoma with multiple metastases to the central nervous system: a case report with a comparative NGS analysis of the primary and metastatic tumours M. Al- Hussaini*, A. Tbakhi, W. Naser, J.Z. Amarin, A. Abi-Sheikha *King Hussien Cancer Center, Jordan Background & objectives: Metastasis from endometrial carcinoma to the central nervous system is rarely encountered. We report a case of a 34-year-old female with dedifferentiated endometrial carcinoma metastasizing to the brain which developed six months later. Methods: There was a well-differentiated endometrial carcinoma, and a second component of poorly differentiated carcinoma, both were positive for PAX-8 immunostain. The CNS metastatic tumour is composed of sheets of undifferentiated tumour cells with islands of immature cartilage, with negative PAX-8 immunostain. These tumours were subject to analysis by NGS to verify the relationship between the different components. Results: NGS of the well-differentiated endometrial carcinoma component showed a pathogenic KRAS mutation (c.35G>A, p.Gly12Asp) with an allele-variant frequency (AVF) of 53.5%, in addition to mutations in the PIK3CA and PTEN genes, as well as a mutation of an unknown significance in the PDGFRA gene. The poorly differentiated component showed a mutation profile similar to the well-differentiated component. However, it lacked the KRAS mutation and harboured two extra mutations in the NRAS (c.182A>G, p.Gln61Arg) and PIK3CA (c.1034A>G, p.Asn345Ser) genes, with an AVF of 33.4% and 32.7%, respectively. Interestingly, the metastatic brain tumour showed an almost identical mutation profile to the poorly differentiated component of the endometrial carcinoma. Conclusion: This is a rare case of metastasizing endometrial carcinoma to the CNS. Molecular testing supported almost identical molecular profiles between the poorly-differentiated endometrial carcinoma, and the metastatic tumour in the CNS, indicating that the brain tumour had possibly originated from the poorly differentiated endometrial carcinoma component. This might have implications for the treatment of similar cases. E-PS-09-017 Determination of microsatellite instability with the Promega™ MSI Analysis System and the Idylla™ MSI assay on 31 endo- metrial carcinomas with deficiency of DNA mismatch repair M.A. Rodríguez Villena*, N. Cadavid Fernández, A. Tenelanda Santillán, C. Ariño-Palao, M.G. Rosas Hernández, E. Moreno Moreno, I. Ruz Caracuel, P. García Abellás, I. Carretero Barrio, B. Pérez Mies *H.U. Ramón y Cajal, Spain Background & objectives: Microsatellite instability (MSI) is due to deficiency of the DNA mismatch repair (MMRd) system. The aim of this study is to define the optimal approach for MSI testing and to clarify discrepancies with MMR protein expression in immunohisto- chemical analysis (IHC). Methods: We selected 31 endometrial cancers (EC) with loss of expression of MMR proteins (MLH1, MSH2, MSH6 or PMS2) to compare two MSI tests, Promega ™ and Idylla ™ . Both recognize mutations in short sequences of specific genes (BAT-25, BAT- 26, NR-21, NR-24 & MONO-27 and ACVR2A, BTBD7, DIDO1, MRE11, RYR3, SEC31A & SULF2) to classify endometrial can- cers as unstable (MSI-H) or stable (MSS). Results: Loss of MMR proteins were distributed in 22 MLH1- PMS2, 4 MSH2-MSH6, 3 MSH6, 1 PMS2, and 1 MSH2-MSH6 & PMS2. With Promega ™ , ten EC were classified as MSS, five as doubtful and sixteen as MSI-H. With Idylla ™ , two EC can- cers were classified as MSS and twenty-nine as MSI-H. Concord- ance between molecular testand IHC were 51,6% for Promega ™ and 93,5% for Idylla ™ . Concordance between Idylla ™ and Pro- mega ™ was 58.1%. Four of ten MSS cases in Promega ™ pre- sented isolated losses of MMR proteins (3 MSH6 and 1 PMS2). The carcinoma with isolated loss of PMS2 was also MSS with Idylla ™ . Conclusion: Idylla ™ MSI assayshows higher sensitivity than Pro- mega ™ MSI analysis, in detecting MSI-H in MMRd EC. Promega ™ misses isolated losses of MMR proteins. Probably, the selection criteria for MSI-H in Promega ™ (more than one gene mutated) is the reason of the low agreement. The discordance between IHC and molecular tests could be explained by sample features, MSS or MSI-low cases with MMRd and because Idylla ™ was developed to analyse MSI in colorectal carcinomas with different range of instability. E-PS-09-018 Ovarian teratoma associated with anti-N-methyl-D-aspartate receptor encephalitis K. Suh*, M. Yeo, S. Choi, K. Kim *Chungnam National University, Republic of Korea Background & objectives: Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is often accompanied by an ovarian tera- toma. A prevailing theory suggests that generation of autoantibod- ies to NMDAR on neurons in the central nervous system is trig- gered by neuroglial tissue in the associated teratoma. Methods: A 15-year-old female presented with a 6-days history of psychological symptoms of mental disorientation for time, person, and place. She had no history of medical or psychiatric problems. Brain computerized tomography (CT) results were unremarkable. A pelvic CT revealed a 3.0-cm, well marginated, heterogeneous, calcified mass in the right ovary with fat components. The patient underwent a right ovarian cystectomy. Results: The cystic ovarian mass measured 2.4x 2.2x 1.8 cm in size. The cut surface showed multiple cysts filled with yellow- ish gelatinous material and some hairs. Microscopically, the mass revealed a mature cystic teratoma showing foci of neuroglial tis- sue with lymphoid aggregates containing germinal centres. Mature neurons were rare, but showed degenerative features including smudged nuclei, cytoplasmic vacuolation, and eosinophilic depos- its. Astrocytes were focally hypercellular. Anti-NMDAR encepha- litis associated with teratoma was considered. Cerebrospinal fluid was positive for Anti-NMDAR antibody. The patient suffered from paraneoplastic neurological syndrome, which included impaired awareness, dysphagia, slurred speech, and dysphoria due to autoim- mune encephalitis. The patient slowly improved with a moderate residual cognitive defect. Conclusion: Here we report a rare case of ovarian teratoma associ- ated with anti-NMDAR encephalitis. The presence of colocalized neuroglial tissue with lymphoid aggregates containing germinal centres and degenerative features within neuroglial tissue in ovar- ian teratomas should be clinically considered as anti-NMDAR encephalitis. S260