ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 positive in some GISTs. Treatment largely depends on the surgery. Adjuvant chemotherapy and radiotherapy have shown only limited benefit in the treatment. E-PS-06-030 Serrated gastric adenocarcinoma developed on a Hyperplastic polyp: a new case K. Ben Lazreg*, R. Jouini, F. Khanchel, I. Helal, S. Fkih, F. Sassi, R. Hedhli, O. Khayat, E. Ben Brahim, M. Sabbah, D. Hadded, A. Chadli *Habib Thameur Hospital, Pathology Department, Tunisia Background & objectives: Gastric serrated neoplasia are recently rec- ognized entities that has been rarely described and poorly character- ized. Fewer than 16 cases of gastric serrated adenomas were reported. We present a less common case of Serrated adenocarcinoma developed on a gastric hyperplastic polyp(GHP). Methods: A 69-year-old woman with no past medical facts, pre- sented vomiting, gastric pain, and loss of weight. An upper endos- copy followed by CT scan were performed. Finally, the patient underwent subtotal gastrectomy with lymphadenectomy and Fin- esterer gastrojejunal anastomosis. Results: The upper endoscopy showed a circumferential antral tumour. CT scan confirmed its presence and showed an associa- tion with perigastric lymph nodes with no hepatic or pulmonary metastases. Gross examination of the later specimen showed an exophytic, ulcerated and infiltrative tumour in the antrum. Histo- logically, there was a Carcinomatous component showing glands with marked serrated neoplastic epithelium resulting in a saw- tooth like architecture. The serrated glands were covered by pleo- morphic cells. The tumour was developed on hyperplastic polyp. No metastases were detected in any of the 30 lymph nodes and the tumour was classified pT3N0. Elsewhere, the gastric mucosa showed chronic gastritis with intestinal metaplasia. Conclusion: Malignant transformation of GHP is very uncommon with an incidence ranging from 0.3 to 3%. Serrated gastric neo- plasia are also exceptional lesions. The first case published was a degenerated serrated adenoma described by Rubio. The invasive carcinoma component of degenerated serrated adenomas, described in literature, may retain the serrated configuration. Immunophe- notypic and molecular features of 9 gastric serrated adenomas were explored. They don’t completely share the same profile of its colorectal counterpart. Therefore, more cases are needed to be published. E-PS-06-031 Collagenous gastritis: clinico-pathological spectrum of 4 cases in a 28 year single centre retrospective study C. Cerezo*, A. Larrea, C. Fuertes, A. Pasco, G. De Lima *Hospital Universitario de Navarra, Spain Background & objectives: Collagenous gastritis is an uncommon dis- ease characterized by the deposition of a subepithelial collagen band thicker than 10 μm and the presence of inflamatory mononuclear cells in the lamina propia. We report the clinical and histopathologic features of this disease. Methods: We performed a single-centre, retrospective study of patients with confirmed collagenous gastritis over a 28- year period of time found in our database. The following param- eters were recorded: patient clinical history, endoscopic find- ings, histologic features, treatments and the presence of other diseases. Results: The study consisted of 4 cases. The median age was 12 years. There was not gender predominance (2 females, 2 males). All of them presented abdominal pain and 2 also had anaemia at diagnosis. The endoscopic findings were: mucosal erythema (n=2), exudates (n=1) and nodularity (n=1). The distribution of collagen deposition was: corpus (n=1), antrum (n=1), corpus and antrum (n=1) and fundus, antrum and cardias (n=1). 3 presented acute gastritis and none had the evidence of Helicobacter pylori infection. One of the patients (25%) had been previously diagnosed of celiac disease (n=1). 3 patients were treated with iron and proton-pump inhibitor and the other one did not received farmacologic treatment. Conclusion: Although collagenous gastritis is a rare clinicopathology entity, familiarity and awareness of the disease is vital for accurate pathological diagnosis. The most frequent symptom at diagnosis is abdominal pain. The endoscopic findings are nonespecific, varying from mucosal erythema, exudates and nodularity. There is a variability in the collagen deposition localization. There does not seem to be asso- ciation between gastritis and Helicobacter pylori infection. Commonly, is associated with other autoinmunne disorders such as celiac disease. E-PS-06-032 A rare case of gastrointestinal stromal tumour (GIST) of the appendix O. McCabe*, C. Dick, E. Macduff, W. Smith *Pathology Department, Queen Elizabeth University Hospital, United Kingdom Background & objectives: Gastrointestinal stromal tumours (GISTs) are the most common gastrointestinal mesenchymal tumours. However, less than 1% of cases arise within the appendix, and few cases are reported in previous literature. We present a case of appendiceal GIST presenting as acute appendicitis. Methods: A 57-year-old male presented with a three day history of lower abdominal pain and nausea. A computed topography (CT) scan showed features of acute appendicitis and an enhancing soft tissue lesion at the appendix tip. The patient underwent laparoscopic appendicectomy. Results: Macroscopically the appendix showed a 10x10mm firm pale area present within the tip. Microscopy showed a nodular aggregate of ovoid, spindled and polygonal cells, with admixed dense pink spheri- cal deposits. The tumour cells showed positive staining with CD117, DOG1 and CD34. Staining was negative with BCL-2, CD56, CD99, S100, SMA, STAT6, synaptophysin, desmin and ALK1, confirming a diagnosis of GIST. The mitotic count was one per 50 high powered fields. After multi-disciplinary team discussion this patient was man- aged as a low-risk GIST with planned radiological interval follow up. The patient has remained well post-operatively. Conclusion: Whilst the majority of GIST’s have a benign clini- cal course, metastasis can occur in 25%. Risk stratification based on clinical and pathological parameters and genetic testing deter- mines subsequent management. This case highlights the impor- tance of awareness of GIST occurring in the appendix. This is a rare entity and the histopathologist plays in crucial role diagnosis and management. E-PS-06-033 Peculiar morphology in colonic adenocarcinoma arising from a traditional serrated adenoma F. Almarii*, S. Stanilescu, L. Welt, G. Lica, I. Popa, M. Bara, G. Halcu *Emergency University Hospital, Romania S225