ECP 2023 Abstracts

S194 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 E-PS-06-005 Gastrointestinal tract lymphomas: a retrospective analysis N. Arı*, S. Uyar Bozkurt, H.K. Türköz, Ç. Ataizi Çelikel *Marmara University School of Medicine, Department of Pathology, Turkey Background & objectives: Gastrointestinal (GI) tract is the most commonly involved site for extranodal lymphomas. This study is a retrospective analysis of GI lymphoma cases in terms of subtype, site of involvement and clinical history. Methods: Thirty-three patients who were diagnosed as GI lym- phoma either with an endoscopic biopsy or resection between 2019- 2022 were included in the study. Pathology reports of these patients were analysed in terms of subtype of lymphoma and localization. Demographic data, patient history (age, sex, history of hematologic malignancies, inflammatory bowel disease (IBD)/celiac disease) and radiological findings were obtained from hospital records. Results: B-cell lymphomas constituted 93,9%(n=31) of the patients whereas small percentage of the cases (6%,n=2) were diagnosed as T-cell lymphoma. Stomach was the most common site of involvement (57,5%,n=19). Majority of patients (63,6%,n=21) was diagnosed as diffuse large B-cell lymphoma. All 3 patients who had gastric extran- odal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT) showed Helicobacter Pylori (HP) positivity. 84,8%(n=28) of the cases presented as primary GI lymphoma whereas 15,1%(n=5) of the patients were considered as secondary involvement of a non-GI lymphoma according to patient history and radiological findings. Only one patient had history of celiac disease whereas none of the patients had a known history of IBD. Conclusion: Chronic inflammation and HP infection are well known risk factors for MALT lymphoma. Consistent with the literature, HP was seen in all 3 cases with gastric MALT lymphoma in our study. Despite the common belief that primary GI lymphomas are rarer than secondary involvement of nodal disease, our sample group consisted of mostly primary cases. This study is an important contribution to litera- ture to achieve better understanding of GI lymphomas, as it constitutes an example for further studies in future. E-PS-06-006 Well-differentiated papillary mesothelioma of the peritoneum: a borderline mesothelioma. Case report of uncommon tumour and literature review R. Ayadi*, E. Braham, F. Loued, H. Ichrak, O. Ismail, A. Ayadi *Hôpital Abderrahmane Mami, Tunisia Background & objectives: Well-differentiated papillary mesothe- lioma of the peritoneum is an uncommon, benign abdominal tumour. There have been fewer than 130 cases reported in the literature today. The diagnosis of this pathology is difficult and based on histological findings. Methods: We report the case of a 57-year old women presented with abdominal pain and vomiting. Clinical examination revealed an abdominal mass induration. Computed tomography showed a 3 larges spherical masses in the abdomen. A gastrointestinal stromal tumour was suspected. A series of biopsy specimens were done. Results: Microscopic examination revealed multiple, uniform, coarse papillae lined by a single layer of bland, flat to cuboidal cells with no signs of atypia were recorded. This papillae were separated by scant loose to collagenous stromal septa. Chronic inflammation and haemorrhage common. Immunohistochemistry stain showed that the tumour cells were positive for calretinin and CK and negative for CD117, CD34 and chromogranine. Based on these histologic and IHC findings, the final diagnosis of Well-differentiated papillary mesothe- lioma of the peritoneum was considered. Conclusion: Establishing a diagnosis of papillairy mesothelioma of the peritoneum is a challenging task, given rarity of the disease and the small number of reported cases in the literature. This tumour is known for local recurrence. It’s agreed that surgery is the only effective treatment. E-PS-06-007 Intraepithelial lymphocytosis doesn’t correlate with dilated intra- cellular space in the oesophagus G. Aydogan*, V. Gorgulu, P. Ergun, S. Kipcak, M. Sezak, S. Bor, B. Doganavsargil *Ege University Faculty of Medicine, Department of Pathology, Turkey Background & objectives: Intraepithelial lymphocytosis (IEL) and dilated intercellular space (DIS) are common in gastroesophageal reflux disease (GERD). We searched for the relationship between them in cases retrieved from Ege University Reflux Clinics database, arranged according to the LosAngeles classification and Lyon consensus. Methods: IEL density was evaluated on hot spot areas, and the average count of 10 High-power filed (HPF) (Olympus-BX50 light microscope, 40x objective, r=0.54 mm) was noted. DIS was measured on digital images taken at 1000x, oil lens, and a total of 100 perpendicular meas- urements were made between the basal-lower prickle layers per patient. Results: All cases including HCs harboured IELs and 7 cases showed eosinophil infiltration (<7/HPF). In 19 cases (13%) IEL was over the 20/ HPF “lymphocytic esophagitis” threshold. The distribution of median IEL density (n/HPF) and mean DIS width (μm) according to clinical groups was as follows; Healthy control (n=12, IEL=5.50±3.53, DIS=0.93±0.22) Erosive GERD (n=74, IEL=10.00±7.07, DIS=1.25±0.25) Non-erosive GERD (n=25, IEL=9.00±8.18, DIS=0.98±0.31) Reflux hypersensitivity (n=15, IEL=7.00±9.50, DIS=0.96±0.27), Functional heartburn (n=19, IEL=8.00±8.72, DIS=1.02±0.29). Erosive GERDs had significantly wider DIS (Anova=9.536,p<0.001) while eosinophil-positive cases showed dilatation as well (median=1.36±0.26 μm, p=0.078, Mann-Whitney U). Overall IEL count didn’t significantly differ among groups (Kruskal Wallis=4.711, p=0.318) and no correlation was found between IEL and DIS (Spear- man=0.081, p=0.334). Conclusion: Despite a slightly higher IEL count in erosive cases, our results provided no solid evidence for a difference between clinical phenotypes, and no association was noted either between IELs and DIS even in lymphocytic esophagitis, in contrast with the previously shown association between eosinophilic esophagitis and DIS. E-PS-06-008 An extraordinary case of “bi-phenotypic” gastric carcinoma: from morphology to molecular characterisation D. Baptista*, I. Gullo, Y. Kim, B. Ylstra, F. Carneiro *Department of Pathology, Centro Hospitalar e Universitário de São João, Porto, Portugal., Portugal Background & objectives: Gastric carcinoma (GC) is highly hetero- geneous both from morphologic and molecular standpoints. The mor- phological features of GC with lymphoid stroma have been associated with Epstein-Barr virus (EBV) infection. We aim to report a case of GC showing remarkable morphomolecular heterogeneity. Methods: A 70-year-old male with a previous history of oral squamous cell carcinoma was submitted to upper endoscopy. A 3cm elevated and sessile lesion (IIa+Is by Paris classification) was found in the subcardic region. The endoscopic biopsy showed (low-grade) dysplasia of gastric phenotype. The lesion was removed by endoscopic submucosal dissection (ESD). Results: Histopathological analysis showed GC with two juxtaposed components: GC with lymphoid stroma (GCLS) and tubulo-papillary adenocarcinoma (TPA). EBV-encoded small RNAs (EBER) in situ hybridization revealed positivity in GCLS component, while TPA was