ECP 2023 Abstracts

S195 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 negative. By immunohistochemistry, both components were mismatch- repair proteins (MMR) proficient. To investigate if the tumour was clonal (despite the two components) or, otherwise, a collision tumour, shallow-whole genome sequencing (sWGS) of both components was performed. Similar amplification/deletion profile was observed, point- ing to a clonal origin of the two components. Since TPA showed lym- phatic invasion and the endoscopic resection was incomplete (verti- cal margin), total gastrectomy was performed. No residual tumour or lymph node metastases (0/50) were observed. Conclusion: The coexistence of EBV+ and EBV- components in GC has been reported only in few cases in which distinct tumour clonal- ity (i.e.collision tumour) was observed, rather than a single tumour with distinct phenotypes. In our case, GCLS and TP components were considered clonal by sWGS, despite showing different EBV status. To our knowledge, this is the first case report of a “bi-phenotypic” GC showing a morphological switch from GCLS adenocarcinoma to TP on the basis of EBV status. E-PS-06-009 Exploring the relationship between tumour grade, tumour size, and lymph node metastasis in colorectal carcinoma R.A. Barna*, M. Cornianu, S. Taban, D. Lazureanu, A. Vaduva, A. Jurescu, O. Vita, A.D. Plopeanu, T. Moga, A. Plopeanu, R. Sirli *Anapatmol Research Center, Victor Babes University of Medicine and Pharmacy, Romania Background & objectives: Colorectal cancer ranks second in inci- dence and mortality in Europe and new prognostic parameters are needed despite management progress. This study aimed to investigate the relationship between tumour size, tumour grade, and the number of lymph nodes (LN) with metastases. Methods: This study enrolled all patients diagnosed with colorectal adenocarcinoma "no other specified" at the County Hospital of Tim- isoara between 2021-2022. Criteria for exclusion: different histological types, multiple tumours, neoadjuvant therapy, or incomplete data. The study recorded tumour size, histological grade (high/low), and lymph node involvement. Statistical analysis was conducted using MedCalc software, including Pearson correlation test, t-test, and chi-square. Results: This study analysed 396 cases of colorectal adenocarci- noma. The average tumour size was 50 mm and the average number of positive regional LN was 3. Compared to low-grade tumours, high-grade tumours had a significantly larger size (t-value=3.1539, p-value=0.001735), but linear regression analysis showed no significant linear relationship between tumour grade and size (p=0.9207). High-grade tumours had a significantly (p=0.006) higher number of positive LN (38 vs 163, respectively, p=0.006) and a lower number of negative LN (14 vs 181) compared to low-grade tumours. The Pearson correlation test indicated a moderate correlation (r=0.1296, p=0.001) between tumour size and the number of LN metastases. Conclusion: This study showed that high-grade CRC tumours have a larger size, a higher number of positive regional LN, and a lower number of negative regional LN, compared to low-grade tumours. Also, there was a moderate correlation between tumour size and the number of LN metastases. Further studies with larger cohorts and analysis of other clinical and histopathological variables are necessary to validate these findings, which could help to predict patient prognosis based on tumour size and biopsy grade of differentiation. E-PS-06-010 Clinical and pathological characteristics of incidental neuroendo- crine tumours of the appendix: a retrospective study of 58 cases D. Beltaifa*, W. Majdoub, A. Baccouche, S. Mestiri, O. Belkacem, L. Jaidane, F. Saidani, A. Bdioui, S. Hmissa *Pathology Department Sahloul, Tunisia Background & objectives: Neuroendocrine tumours encompass a diverse array of tumour pathologies, ranging from indolent, incidental tumour to poorly differentiated and aggressive carcinomas. Our aim is to describe the clinical and pathological aspects of appen- diceal neuro endocrine tumours (A-NETs). Methods: A total of 58 cases of A-NETs were retrospectively ana- lysed from the cancer registry of Central Tunisia spanning a 12-year period (2010-2022). Epidemiology, clinical presentation, and histopathology features were evaluated. Immunohistochemical confirmation was required, including neuroen- docrine staining and Ki-67 proliferative index. A-NETs were subdivided into grades G1, G2, and G3 according to the mitotic index and Ki-67expression. Results: A female predominance was observed, with 34 females and 24 males. The mean age was 34.5 years, with a paediatric frequency of 15.5%. A-NETs were incidentally discovered in all cases, with 88% occur- ring during the management of acute appendicitis and 12% detected in other pathologies. No cases of carcinoid syndrome were observed. On macroscopy, the mean diameter was 1.88 cm, and 84.5% of A-NETs were located at the tip of the appendix. Microscopically, A-NETs revealed typical features of well-differen- tiated neuroendocrine tumours. Immunohistochemistry revealed positive staining for chromogranin A and synaptophysin in 81% and 69% of cases, respectively. A-NETs were low or intermediate grade, with 85% of cases being Grade 1. Conclusion: Various clinical and pathological parameters have been identified as significant prognostic factors in A-NETs. Therefore, it is crucial to include size, the presence of lymphovascular invasion, grade, and infiltration staging in the pathology report for each indi- vidual case to provide a comprehensive description and ensure optimal management. Although the pathology features of A-NETs are well-known, studies in molecular biology are not common. Some authors have reported multiple mutations, including TP53, PTEN, SMAD4, and EGFR, in only a few cases. E-PS-06-011 Clinicopathological study of gastrointestinal leiomyoma: about 5 cases D. Beltaifa*, F. Saidani, O. Belkacem, T. Tlili, A. Baccouche, A. Bdi- oui, S. Hmissa, S. Mestiri *Pathology Department Sahloul, Tunisia Background & objectives: Leiomyoma is a rare benign mesenchymal tumour accounting approximately for one-third of all mesenchymal neoplasms in the gastrointestinal (GI) tract. The objective of this study is to describe the clinical and histopathological features of leiomyoma in the GI tract. Methods: We analysed five cases of leiomyoma in the GI tract from the Cancer Registry of the Center of Tunisia between 2016 and 2022. The leiomyomas were resected from the stomach, small intestine, and colorectal regions. Immunohistochemical confirmation was required, including desmin and/or smooth muscle actin immunostaining. Stain- ing for CD117 and DOG1 was conducted to rule out Gastrointestinal Stromal Tumours (GIST). Results: We identified 5 patients,3 men and 2 women, with a median age of 47.5 years (range 16-65 years). The tumours were located in the gastric (40%) and colorectal regions (40%) and small intestine (20%). On gross examination, the median size was 6.4 cm (range 1-13 cm) on macroscopy. Microscopically, the tumour consisted of fascicles of