ECP 2023 Abstracts

S216 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 gastrointestinal tract, but there is no consensus on this issue. In this study, we aimed to evaluate those cases diagnosed in the gastrointesti- nal tract in our department. Methods: 25 patients who applied to our hospital between 2010-2019 with different clinical complaints that had various diagnoses and also accompanying vascular lesions such as angiodysplasia, arteriovenous malformation, haemangioma, and Kaposi sarcoma in the gastrointes- tinal tract were reevaluated. 19 surgical resections, 4 colonic polypec- tomies, and 2 endoscopic biopsies were sent to our laboratory. All materials were reevaluated by 2 experienced pathologists. Results: Of 25 patients, 16 were male and 9 were female. The age dis- tribution was 19-83 (mean 58). Angiodysplasia was found to be primary in 6 of the 13 gastric resections, incidental in 3 sleeve gastrectomies, and as an accompanying lesion in 4 other malignancies. Kaposi sar- coma was diagnosed in 1 gastric biopsy. Angiodysplasia was observed in 4 hemicolectomies and 4 colon polyps. A cavernous haemangioma was found in 1 colectomy, and a haemangioma in 1 rectal biopsy. The lesions were observed as thin/thick-walled malformative vascular struc- tures with abnormal dilatation and irregular folding in the submucosa, and also in all the organ walls including the subserosa in some cases. Conclusion: Vascular lesions of the gastrointestinal tract, such as angi- odysplasia and arteriovenous malformation, of which the true incidence is unknown, are seen in many cases presenting with gastrointestinal bleeding. They can also be seen as accompaniments in patients oper- ated for other reasons, as in our study. Our other interesting finding is that angiodysplasia can be seen incidentally in sleeve gastrectomies. We think that increasing awareness of these lesions and evaluating all gastrointestinal materials from this perspective may increase the actual incidence. E-PS-06-091 Appendiceal diverticulosis with inflammatory fibroid polyp and hyperplastic polyp, a rare case report A. Vergili*, N. Ekinci, C. Tavusbay *Izmir Katip Celebi University, Ataturk Training and Research Hospi- tal, Department of Pathology, Turkey Background & objectives: Appendiceal diverticulosis is a rare dis- ease that is most commonly asymptomatic. It can accompany many benign or malignant tumours. Inflammatory fibroid polyps are benign mesenchymal lesions rarely seen in the appendix. Hyperplastic polyps are also rarely encountered in the appendix. Methods: A 61-year-old male patient had a left hemicolectomy due to moderately differentiated adenocarcinoma located in the rectosigmoid area 5 years ago. Elective appendectomy was decided for the patient in the oncology council because of the radiological diagnosis of mucocele in the distal appendix. A 9 cm long and 0.8 cm wide appendectomy material was sent to our laboratory. Results: Macroscopically, many diverticular structures within mucoid con- sistency were observed at the distal end of the appendix. In microscopic examination, formation of multiple diverticula was noted characterized by invagination of mucosa through muscularis propria. In addition, on the wall of one of these diverticula, a 2 mm diameter, submucosal, well-cir- cumscribed lesion was incidentally observed. It was characterized by thin- walled vascular structures with spindle cell proliferation and prominent eosinophilic infiltrate. Immunohistochemically, spindle cells were positive with CD34, vimentin and fascin, and this lesion was thought to be com- patible with an “inflammatory fibroid polyp”. After the total submission of the appendix, a "hyperplastic polyp" in a 2 mm focus was also found. Conclusion: In the literature, many benign and malignant tumours and lesions accompanying appendiceal diverticulosis have been reported. For this reason, to avoid missing such lesions, new sampling for neo- plastic or non-neoplastic lesions should be performed if an appendiceal diverticulum is diagnosed macroscopically or microscopically. Since the association of the appendiceal diverticulum with an appendiceal inflammatory fibroid polyp and a hyperplastic polyp has not been reported in the literature, in our opinion, our case is worth presenting. E-PS-06-092 Expression of neuroendocrine markers in SWI/SNF deficient colo- rectal carcinomas. P. Vlachou*, F. Dolkiras, N. Stavrinou, E. Spiteri, E. Athanasiou, A. Therapontos, M. Lenos *Department of Pathology, Evaggelismos General Hospital Athens, Greece Background & objectives: We present the case of an 87yo woman with a mass in her ascending colon. The aim of this abstract is to demonstrate that the expression of neuroendocrine markers in SWI/ SNF-deficient carcinomas does not necessarily categorise them as neu- roendocrine carcinomas. Methods: A right hemicolectomy specimen was received. Upon gross examination, the tumour was of 7,9cm in greatest diameter and invaded the surrounding adipose tissue with ulceration and invasion of the adven- titia. Hematoxylin/eosin staining was used in the submitted sections. Immunohistochemistry for CK8/18, synaptophysin, chromogranin A, p53, retinoblastoma, MLH1, PMS2, BRAFV600E (Ventana/ clone VE1), INI-1, SMARCA4/BRG and SMARCA2/BRM was also performed. Results: The neoplastic cells were having a partly undifferentiated histology, with focal pleomorphism and were arranged in sheets with central coagulative necrosis. The rest of the tumour cells showed eosin- ophilic-rhabdoid morphology. Immunohistochemistry was noteworthy for the expression of CK8/18, diffuse and moderate expression of syn- aptophysin and focal-weak chromogranin A expression. Protein p53 was overexpressed consistent with a mutated pattern, retinoblastoma protein was retained. There was loss of the proteins MLH1, PMS2, while mutation specific antibody BRAFV600E (Ventana/ clone VE1) was expressed, findings consistent with a microsatellite unstable carci- noma of the colon.Nuclear expression of INI-1 and SMARCA4/BRG was retained, while nuclear expression of SMARCA2/BRM was lost, suggestive of a SWI/SNF-deficient colorectal carcinoma. Conclusion: Based on both immunohistochemical and phenotypical characteristics the tumour was characterised as SMARCA2/ BRM defi- cient undifferentiated colorectal carcinoma with microsatellite instabil- ity. The pathologist should be aware of the potential expression of neu- roendocrine markers in SWI/ SNF- deficient carcinomas which should not be categorised as neuroendocrine carcinomas unless they also have other neuroendocrine phenotypical characteristics. E-PS-06-093 Early stage (T1) colorectal cancer (CRC) following endoscopic resection in screening and non-screening populations; rates of residual tumour and lymph node metastasis (LNM) following oncological resection C. Ward*, N. Swan, N. Nolan, M. Cotter, D. Gibbons, K. Sheahan *Saint Vincent’s University Hospital, Dublin, Ireland Background & objectives: Oncological resection following endoscop- ically resected T1 CRC is considered on a case-by-case basis, given potential surgical risks and low rates of LNM (8-10%) and recurrence (3.3%). We evaluated rates of residual mural disease and LNM in screening and non-screening populations. Methods: We analysed a database of T1 cancers diagnosed in polypec- tomy specimens in screening cases since 2013 and a non-screening cohort since 2018. Histopathological reports were reviewed for risk factors such as deep submucosal invasion (DSI) >1mm, lymphovas- cular invasion (LVI), tumour budding, grade and margin status. Rates