ECP 2023 Abstracts

S199 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 Case 1: Focal intramucosal carcinoma, widespread clear cell change, and high-grade dysplasia arose in the base of tubulovillous adenoma were identified. Case 2: Conventional glandular areas with extensive clear cell change and poorly differentiated areas of invasive adenocarcinoma were observed. Additionally, amphicrine-type neuroendocrine dif- ferentiation was detected, showing synaptophysin and INSM-1 posi- tivity throughout the tumour. Both lesions were microsatellite stable. Clear cell areas were negative with PAS, Alcian Blue, MUC2, and MUC6 and focally positive with MUC5AC stains. Conclusion: Tumours with clear cell change can be primary to the colorectum. However, there is limited information regarding the causes and prevalence of this phenomenon. Especially on a biopsy specimen, being aware of this entity has paramount importance to avoid misdiagnosis. Histomorphological patterns and immune profile assist to exclude metastasis from other organs. Our cases are examples of extensive clear cell change in colorectal neoplasms, one of which arises on an adenoma and the other invasive carcinoma shows neu- roendocrine differentiation. E-PS-06-024 Anaplastic lymphoma of the colon: a very rare location O. El Mnif*, A. Zehani, A. Ayari, B. Chelly, H. Azzouz, I. Chelly, K. Bellil, S. Haouet *La Rabta pathology department Tunis, Tunisia Background & objectives: Anaplastic lymphoma is a rare and aggres- sive of non-Hodgkin lymphoma. Colonic localization by anaplastic lym- phoma is extremely rare, with only a few cases reported in the literature We report a case of colonic anaplastic lymphoma of a 17-year-old male. Methods: We analysed the medical file of a 17-year-old patient with a medical history of diffuse large cell lymphoma diagnosed 6 months ago and still undergoing treatment, operated on for colocolonic intussuscep- tion following an acute abdominal presentation. A hemicolectomy was then performed highlighting a colonic mass. Representative sections of the mass were examined under H&E and immunohistochemical stains. Results: On gross examination presence of a budding mass with a fleshy white appearance that infiltrates the subserosa. Microscopic examination under H&E revealed a lymphoid prolifera- tion of diffuse architecture with anaplastic large cells with abundant cytoplasm and horseshoe shaped nuclei. The proliferation infiltrates the entire colonic wall and presents some ulceration on the surface with multiple perineural sheathing and numerous vascular emboli. Twente lymph nodes were sampled, 17 were infiltrated. An immunohistochemical study was performed showing that the tumour cells express focally the CD30 antibody and ALK antibody in a diffuse way. the rest of the antibodies: CD4 CD8 CD5 CD3 CD20 CD2 CD79 and CK were negative. Conclusion: Anaplastic lymphoma of the colon is an extremely rare and aggressive neoplasm that poses diagnostic challenges. It can mimic other malignancies, such as adenocarcinoma or other high-grade lym- phomas requiring careful histopathological examination and immuno- histochemical staining for accurate diagnosis. E-PS-06-025 Glomus tumour is a rare gastric mesenchymal tumour: a case report Z. Fayed*, D. Sweed *National Liver Institute, Menoufia University, Egypt Background & objectives: Glomus tumours (GGTs) account for fewer than 1% of all gastrointestinal soft tissue tumours. GGT develops as a solitary, intramural nodule that radiologically mimics GIST. Lack of specific clinical, radiographic, and endoscopic findings makes the presurgical confirmation difficult. Methods: We present a case of a 24-year-old Egyptian female who complained of a hemodynamically significant but self-limiting melena. Upper endoscopy and computed tomography revealed a mesenchymal antral mass, suggesting GIST. The patient had a distal gastrectomy with Roux-en-Y reconstruction. Results: Macroscopically, a well-circumscribed intramural mass meas- uring 2.3 cm in the largest size and covered by ulcerated mucosa. The cut section was soft, brown, and had haemorrhagic areas. Microscopic examination revealed a non-capsulated intramural neoplastic growth with branching capillary-sized vessels lined by monomorphic cells organized in sheets and nests with eosinophilic cytoplasm. The tumour was expanding to the mucosa, causing ulceration but no serosal affec- tion. There was no nuclear atypia, mitosis, or lymph vascular invasion. The tumour was totally excised. Tumour cells expressed SMA but did not express Pan CK, CD 117, chromogranin, or S100. The enhanced vascular component was highlighted by CD34. Conclusion: A gastric glomus tumour is a rare pathologic entity with potentially benign behaviour. Despite a few reported cases, it is still missing in the differential diagnosis of a gastric intramural mass in the pre-surgical / pre-histopathology status to date. Long follow-up is recommended to exclude less like the possibility of recurrence or metastasis. E-PS-06-026 A rare case of epidermoid cyst of the cecum A. Firrincieli*, E. Nardi, G. Alemanno, L. Pugliese, L. Messerini *University of Florence, Italy Background & objectives: Cecal epidermoid cyst is a rare and benign lesion; with only 12 other cases reported in the literature. Due to its rarity, the pathogenesis remains unclear. The case of epi- dermoid cyst in symptomatic patient, treated by ileocecal resection, is presented. Methods: A 28-year-old woman was admitted to hospital with abdomi- nal pain, stable vital signs and no history of previous surgery. CT and MRI scans were performed and a large cystic mass in the anterior por- tion of the pelvic region was detected. Imaging techniques managed to localize the site and dimensions of the neoformation; however, they did not provide a conclusive diagnosis. Results: The differential diagnosis was made with appendiceal mucocele, duplication cyst or endometriotic formation. Laparoscopic right hemicolectomy was performed, and the formation was resected. No complications occurred during surgery as the mass did not pre- sent any adhesion with the surrounding organs such as uterus, bladder, sigma, and ovaries. The specimen was then evaluated both macroscopically and microscopically. The macroscopic evaluation showed an irregular extraluminal cystic lesion arising from the cecal wall of 104 x 83 x 68 mm. The micro- scopic examination revealed a cystic wall lined by keratinized stratified squamous epithelium. No malignant findings were identified. Thus, the histopathologic evaluation leads to the final diagnosis of epidermoid cyst. Conclusion: Epidermoid cysts are rare benign neoformation that can be acquired or congenital. They can vary both in their clinal and instrumental presentation. The lesion can be associated with non-specific symptoms or be asymptomatic showing a wide het- erogeneity both in sex distribution and age. Imaging techniques are useful for differential diagnosis with other neoplasms or abdominal masses, but the final diagnosis can be made only after the com- plete surgical excision of the neoformation and its histopathological examination.