ECP 2023 Abstracts

S115 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 (p<0.001). While both PTB and ITB were found to be associated with histological subtype, grade, and lymph node metastasis (LNM), PTB was also correlated with the level of invasion and metastasis (p<0.005). Univariate survival analysis revealed that ITB, PTB (p<0.001), LNM (p values <0.001), DR, and stage (p<0.03) as risk factors for poor prognosis. ITB, PTB, and lymph node metastasis were independent prognostic factors in multivariate Cox-regression analysis. Conclusion: Our findings support that the evaluation of TB accord- ing to ITBCC criteria can be performed to stratify patients with gastric cancers for treatment and prognosis. In addition, the relationship among TB, DR, and lymphocyte infiltration in the tumour area observed in our study warrants further research with larger patient series to determine the role of a scoring system consisting of these three parameters in determining the behaviour of gastric cancers. PS-18 | Poster Session Neuropathology PS-18-001 Morphological analysis of intraepithelial nerve fibre density in Par- kinson’s disease patients treated with levodopa-carbidopa intesti- nal gel infusion (Duodopa system) E. Izycka-Swieszewska*, K. Buczkowski, R. Piekarski, J. Slawek *Medical University of Gdansk, Poland Background & objectives: A prevalence of small fibre neuropathy in Parkinson’s disease patients treated with Duodopa system is higher than in general population. An objective is to determine the nerve fibre density and the influence of vitamin supplementation on development of neuropathy. Methods: 21 patients (age:50-78) with Parkinson’s disease (duration 6-25y) treated with Duodopa System for one year. Skin punch biopsies (3mm core) taken from thigh and lower leg at the onset and after one year. Ten randomized patients received supplementation of B vitamins and folic acid. Histological slides were stained with H-E and immuno- histochemically with PGP 9.5 with a routine procedure. Results: Intraepidermal nerve fibre density (IEND) was assessed according to the European Federation of Neurological Societies guidelines. Groups with and without vitamin supplementation pre- sented no significant differences in initial IEND (thigh: 0,76±0,28/ mm vs 1,18±0,62/mm, p=0,09; calf: 0,39±0,26/mm vs 0,59±0,42/mm, p=0,32) . The group without supplementation showed a statistically significant decrease of IEND in the skin after one year (0,48±0,25/ mm vs 1,18±0,62/mm, p=0,003), compared to the baseline biopsy. Such differences were not found in the lower leg sections in this group (0,39±0,35mm vs 0,59±0,42/mm, p=0,18). However, no statistically significant differences in density were observed in the group with vitamin B supplementation (thigh: 0,78±0,43/mm vs 0,76±0,28/mm, p=0,51; lower leg: 0,46±0,36/mm vs 0,39±0,26/mm, p=0,51). Conclusion: The observed reduction of IEND may reflect the progres- sion of a small fibre neuropathy in Parkinsonian patients treated with Duodopa system. In parallel, oral supplementation of B-group vitamins possibly has a preventive effect for neuropathy progression. The longer observation on the bigger group of patients is needed. PS-18-002 The impact of methylome implementation on neuropathology: experience of two referral hospitals S. López*, C. Rodríguez Jiménez, L. Fernandez Ariati, E. Rubio Martín, R. Moreno Velasco, M. Burdiel Herencia, O. Pernía Arias, I. Ibáñez de Cáceres, N. Rodríguez Salas, A. Patiño García, I. Este- ban Rodríguez, J.I. Echeveste, C. Lavarino, Á. López Janeiro, C. Rodríguez Antolín *Hospital Universitario La Paz, Spain Background & objectives: Genome-wide DNA methylation profil- ing is valuable tool to refine diagnosis in neuro-oncology, although they are not universally available. We investigated the impact of DNA methylation-based classification on neuropathological diagnosis in two tertiary referral hospitals. Methods: We analysed brain tumours diagnosed from January 2022 to March 2023 at University Hospital La Paz (Madrid, Spain) and Clínica Universidad de Navarra (Pamplona, Spain). Tumours submitted to DNA methylation-based (EPIC-850K-BeadChip-Array, Illumina) clas- sification (Brain tumour classifier v12.5 https://www.molecularneuro - pathology.org ), were selected for further analysis. We recorded pre-test histopathologic diagnosis and associated WHO-grade and additional diagnostic information provided by the methylome analysis. Results: Ten out of 103 (9.7%) brain tumours underwent DNA methyl- ation analysis. Most patients were younger than 30 years of age (mean = 22 years p25-p75=13-24,75). Inability to perform a specific entity diagnosis was the reason to perform methylome analysis in all tumours. Histologically, three tumours were classified as glioneuronal tumours, 2 were diffuse gliomas and 5 were found to be unclassifiable. Nine out of 10 tumours were low grade (G1 or G2), none harboured IDH1/2 or ATRX mutations. The Brain tumour classifier score was greater than 0.5 in 8 out of 10 cases. The diagnosis of 5 cases was refined after methylome analysis. Of note, tumour grades remained unchanged. Conclusion: DNA methylation-based classification was required in a small subset of all brain tumours diagnosed, mostly for difficult-to- diagnose tumours in paediatric or young adult patients. Methylation analysis improved diagnostic accuracy in 50% of cases, demonstrat- ing its utility as complementary tool to refine diagnosis in a subset of highly selected patients. Importantly, methylome diagnostic refinement did not modify the final WHO tumour grade. Funding: GETTHI Ramón de las Peñas Grant PS-18-003 Clinico-pathological spectrum of intracranial mesenchymal tumours, FET::CREB fusion-positive - case series T. Pancsa*, R. Laxton, L. Bhaw, C. Fisher, A. Niblett, D. Hughes, E. Maratos, K. Ashkan, M. Gallagher, S. Al-Sarraj, A. King, I. Bodi, Z. Reisz *University of Szeged, Department of Pathology, Szeged, Hungary Background & objectives: Intracranial mesenchymal tumour (IMT), FET::CREB fusion-positive is a provisional tumour type in the 2021 WHO Classification of CNS tumours awaiting further clarification. Here, we present the clinicopathological findings, therapeutic manage- ment and follow-up data of six cases. Methods: A retrospective departmental study found six intracra- nial tumours (9-65 years, M:F=5:1) with molecularly confirmed FET::CREB fusion. All tumours were extensively investigated by immunohistochemistry and further analysed by multimodal panel (covering 305 DNA and 76 RNA targets)/TruSight RNA Pan-Cancer Panel (targeting 1385 genes) and DNA methylation array. Cases were reviewed for histological and radiological features, therapeutic manage- ment and follow-up data. Results: Histologically, most tumours showed vague lobular arrange- ment, sclerotic/hyalinised areas and pseudo-angiomatous spaces. One case displayed astroblastomatous-type rosettes. Desmin, CD68 and PLAP were positive in all except one case. The most frequent EWSR1 fusion partner was the CREM (3 cases) followed by CREB1 (2 cases) and ATF1 (1 case). One jugular foramen tumour was profiled as “angi- omatoid fibrous histiocytoma (AFH)” with multiple CNV alterations, while the rest showed no match by DKFZ Sarcoma classifier (v12.2) and had a relatively balanced genome. Five cases with complete surgi- cal excision showed no tumour recurrence on follow-up. The jugular foramen tumour underwent surgical debulking and it recurred in 16 months with multiple spinal tumour implants.