ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 contexture in relation to specific treatments will inform future treatment decisions. Funding: This work was supported by an Alpe d’HuZes/KWF program grant (KWF UL 2013-6311)]. PS-07-019 H3K27me3 immunohistochemical loss predicts response to neo-adjuvant chemo-radiotherapy (CRT) in patients with locally advanced rectal adenocarcinoma N. Caldonazzi*, P.C. Rizzo, S. Ammendola, G. Turri, C. Pedraz- zani, A. Scarpa, V. Barresi *Department of Diagnostic and Public Health, University of Verona, Italy Background & objectives: Patients with locally advanced rec- tal cancer are treated with neo-adjuvant chemo-radiotherapy to improve resectability and decrease the probability of recurrence. This study aims to assess whether H3K27me3 immunostaining in pre-treatment biopsies of rectal adenocarcinoma may predict response to neo-adjuvant CRT. Methods: We assessed H3K27me3 immunostaining in 43 pre- treatment endoscopic biopsies of locally advanced rectal car- cinomas treated with neo-adjuvant CRT and correlated it with Tumour Regression Grade (TRG) measured using Dworak system in the following surgical specimen. H3K27me3 immunostain was classified: i) retained (≥ 5% stained neoplastic cells); ii) lost (> 95% stained neoplastic cells); iii) inconclusive (unstained normal and neoplastic cells). Results: H3K27me3 immunostaining was lost in 18 cases, retained in 17 and inconclusive in 8. All tumours with retained H3K27me3 expression had complete tumour regression (TRG 4/5). H3K27me3 loss was significantly associated with absent/ partial tumour regression (TRG 0/1/2) in surgical specimen (P=0.0015) Conclusion: Due to the lower probability to respond to neo-adju- vant CRT, a "watch and wait" approach to avoid side effect of surgery should be used with caution in patients with rectal carcino- mas with H3K27me3 loss in the endoscopic pre-treatment biopsy. PS-07-020 NET G3 of the digestive system: clinico-pathological and molec- ular features of 7 cases L. Casiccia*, R. Maragliano, M. Testa, F. Sessa, S. La Rosa, S. Uccella *Institute of Pathology, Dept. of Medicine and Surgery, University of Insubria, Varese, Italy Background & objectives: Grade 3 Neuroendocrine Tumour of the digestive system (DS-NET G3) is a recently recognized entity exhibiting well differentiated morphology and high proliferation rate. Our study aimed to analyse the morphophenotypical, molecular and clinical features of 8 DS-NETs G3. Methods: We collected 8 DS-NETs G3 in our institution between 2015 and 2018. Clinical records and pathological samples were available for further analysis. The histopathological review was performed according to the upcoming WHO classification for Neu- roendocrine Neoplasms. Immunohistochemistry for Chromogranin, Synaptophysin, INSM1, p53, Rb, p16, SSTR2A, DAXX/ATRX, Cyclin D1, Ki67 was performed. Next Generation Sequencing (NGS) was executed on 4 cases. Results: Our cases included 3 pancreatic NETs (PanNETs) and 5 gastrointestinal NETs (1 gastric, 1 ileal, 1 appendicular, 1 cae- cal, 1 rectal). They were all characterized by a well differentiated morphology and a Ki67 index >20% (mean: 25%, range: 20-40%). General neuroendocrine markers were intensely and diffusely posi- tive in all cells. SSTR2A showed membranous immunoreactivity in 6 of 8 cases. p53, Rb1 and p16 expression weren’t altered in any case, whereas Cyclin D1 was frequently overexpressed. Molecular analysis did not reveal any abnormality in key cancer genes, includ- ing TP53 and RB1 genes. The mean follow-up of patients was 24 months and no disease-related death was recorded. Conclusion: Our case series recapitulates the clinicopathological and molecular characteristics of G3 NETs of the digestive system. This analysis highlights common features of these neoplasms, arisen in different sites, useful to distinguish them from neuroendocrine carcinomas occurring in the same locations. PS-07-021 PINK1 analysis in colorectal adenocarcinoma and their respec- tive hepatic metastasis with clinical relevancy J.C. Celis Pinto*, D. Corte-Torres, A. Vallina, A. Alonso Fernán- dez-Velasco, I. Fernandez-Vega *Hospital Universitario Central de Asturias, Spain Background & objectives: PTEN-induced-kinase-1 (PINK1) is essential for maintaining mitochondria metabolism and survival in colon cancers. Higher PINK1 expressions were correlated with worsened survival. Our aim was to study the immunoexpression of PINK1 in samples from colorectal adenocarcinoma and their respective hepatic metastases. Methods: Ninety consecutive patients with colon adenocarcinoma and subsequent hepatic metastasis surgically removed between 2005 and 2022 were studied. Tissue arrays were produced using a 2 mm diameter needle. Immunohistochemical studies were conducted and analysed by the H-Score method. Statistical analysis of these findings was carried out using the SPSSv25; p<0.05 program. Results: Positive immunoexpression was detected in more than 95 percent of both primary tumours and their hepatic metastases with significant median differences (82,27 ± 48,75 vs 91,29 ± 49,59; p= 0,034). A positive correlation was identified for PINK1 immunoexpression between primary and metastatic tumours (r= 0,352; p=0.001). A cut-off of 100 points of PINK1 in primary samples and 110 in metastatic samples segregated patients into groups with a significant different prognosis. For instance, more than 110 points of PINK1 immunoexpression in patients with metastatic samples combined with more than 25 mitotic figures per 10 high-power-fields had a worse global survival (105,25 ± 14,04 vs 54,95 ± 10,47 months; p=0.018). Conclusion: Overexpression of PINK1 was observed in hepatic metastasis versus primary colon adenocarcinoma with a positive correlation. Defined cut-off with clinical relevance for PINK1 immunoexpression in hepatic metastasis and primary colon adenocarcinomas was identified. Funding: Sakura Finetek Spain PS-07-023 The usefulness of Cycline D1 in diagnostics of naive, CD117/ DOG1 positive gastrointestinal stromal tumours (GISTs) – cor- relation with other histological and immunohistochemical factors M. Lenarcik*, M. Polkowski, P. Wieszczy, A. Mróz *CPME, Poland Background & objectives: The aim of the study is to correlate Cycline D1 expression with size and mitotic activity assessment using PHH3 and Ki67 stainings in determining high risk tumours. S96