ECP 2023 Abstracts

S225 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 Conclusion: It seems that immunomarkers expression in ALM shows important disparities that need to be known, compared to the known patterns in primitive tumours. Here is the first analysis of a large panel including 18 immunomarkers on a significant number of ALM. The complete statistical analysis that will include clustering analysis, k-means, and combinatorial analysis should be able to identify which markers or marker combinations could be the most robust in a daily practice of ALM diagnosis. E-PS-07-025 Solid pseudopapillary neoplasm of the pancreas – case report M. Jikurashvili*, I. Nedkov Ivanov *CSD-Georgia, Georgia Background & objectives: Solid pseudopapillary neoplasm of the pancreas is a rare tumour with unclear cell of origin, affecting pre- dominantly female individuals. It represents less than 2% of exocrine pancreatic tumours and is associated with favourable prognosis. Methods: We report a case of a retroperitoneal mass, observed in a female individual in her 6th decade of life. The imaging showed an infiltrative tumour involving the kidney, aorta, pancreas and spleen. The management of the patient included a diagnostic biopsy followed by surgical treatment (distal pancreatectomy). Results: H&E sections from the diagnostic biopsy revealed fibro-fatty tissues with discohesive, solid, partly pseudopapillary tumour com- posed of monomorphic, round, eosinophilic cells with angular and grooved nuclei and intracytoplasmic hyaline globules. Only a few mitotic figures were detected. The tumour cells were positive for CD10, S100, beta-catenin (nuclear), vimentin, CD56 and focally on Cyclin D1, NSE. E-cadherin expression was lost. Ki67 index was <5%. The post-operative sample revealed infiltrative intrapancreatic 6cm tumour with solid-cystic areas and haemorrhage without necrosis and inva- sion in spleen. Microscopy showed the same features described in the biopsy. In addition: foamy macrophages, cholesterol crystals and cal- cifications. No high-grade transformation, neural or vessel invasions were seen. Conclusion: The overall diagnosis was a solid pseudopapillary neo- plasm of the pancreas with low malignant potential. The long-term prognosis of this tumour is generally excellent for localized, metastatic and even recurrent disease after complete surgical resection. This rare tumour may be difficult to identify in a small biopsy and immunohistochemistry plays vital role in the diagnostic process. The striking sex and age distribution with the gross features described above are also important criteria to consider. E-PS-07-026 Unexpected pathological lesions encountered in the gall bladder: a surgical pathology review of 5,636 consecutive gall bladder surgi- cal specimens R. Kanthan*, S. Kanthan *University of Saskatchewan, Canada Background & objectives: The gall bladder, a common ‘low-stakes’ surgical pathology specimen received for calculous/non-calculous related inflammations, rarely has unexpected lesions that are extremely challenging for accurate diagnosis. This study aims to discuss 43 such cases encountered in our routine surgical pathology practice. Methods: A retrospective LIS computer search of “gallbladder’ sur- gical pathology cases for the last twenty years was undertaken. The pathological reports were reviewed and catalogued. Cases with the final diagnosis of any uncommon pathology excluding routine inflammation/ cholesterol polyps/cholesterolosis were identified. These selected cases were categorized by age and sex and a detailed in-depth review of their pathological diagnosis was carried out. Results: 352,253 cases were processed to yield 5,636 gall bladder reports. Review of these reports identified the majority of the cases to be varied degrees of acute or chronic inflammation, mostly associated with calcu- lous disease. These lesions occurred in adults ranging from 23-83 years with a strong female predilection. Adenomyomatous hyperplasia was seen in 52 cases. Unexpected lesions encountered included Biliary Intraepi- thelial Neoplasia [8]: high-grade, multifocal [4] and low grade [4]; Gall bladder cancers [25] –primary [18] metastatic renal cell carcinoma [1] and secondary involvement from adjacent cancer of the hepatic flexure of the colon [6] ; Heterotopia-gastric [2], hepatic[2] and tubulopapillary neoplasms [6]: non-invasive [4] and with invasive carcinoma [2]. Conclusion: Our study highlights the rarity of uncommon patholo- gies in the gall bladder. It is important to be aware of these lesions as accurate histological identification is vital, as this determines the next step treatment strategies for the patient as in gall bladder cancers. The recently described tubulopapillary lesions need accurate recognition to avoid overtreatment in cases that have no ‘true’ invasive component. We recommend the entire gall bladder to be processed for evaluation in all cases with any unexpected pathology. E-PS-07-027 Exploring Syndecan-1 expression profile in neuroendocrine tumours of the grastointestinal tract and pancreas E. Koniaris*, A. Kataki, I. Angelioudaki, A. Mitrousias, A.G. Tzingou- nis, A. Charchanti, G. Zografos, M. Konstadoulakis, G. Kafiri *Pathology Departmant, General Hospital of Athens ’Hippocratio’, Greece Background & objectives: Neuroendocrine neoplasms (NENs) can be developed in different sites along the gastrointestinal tract (GI) and are classified as tumours (NETs) and carcinomas (NECs). The present study is focusing on exploring the expression profile of syndecan-1 protein (SDC-1). Methods: Study’s cohort consisted of 29 NETs mean age 61.93±2.0 mean age 65.3±2.39, 20 located in pancreas (pNET) and 9 in the GI (giNEC); 20 NECs: 11 located in pancreas (pNEC) and 9 along GI (giNEC); and 7 MANEC mean age 67.56±2.62, 2 of which are in pancreas (pMANEC). Results: SDC-1 expression was detected immunohistochemically and both percentage of positive cells and intensity were scored in lesions’ as well as in normal adjacent tissue. Their multiplication score was used in statisti- cal analysis. SDC-1 expression was both membranous and cytoplasmic in epithelial cells. A shift from membranous to cytoplasmic expression was observed from normal to lesion’s stroma. SDC-1 expression wasn’t detected in giNETs lesions’ epithelium whereas, epithelium expression was limited to cell membrane in pNETs. In giNECs higher expression of SDC-1 was observed in cancer epithelium compared to pNECs, still without reaching a statistically significant difference. No protein expression was spotted in normal adjacent stroma. Findings were similar in MANEC. Conclusion: The herein presented data indicate that in these rare neo- plasms SDC-1 protein expression profile varied based to their site of origin. In addition, the observed shift of SDC-1 expression from the cell membrane to the cytoplasm further support that its loss of function at the cell-surface may facilitate cancer progression and the development of invasive and metastatic disease. Funding: NeXT E-PS-07-028 Undifferentiated carcinoma of the pancreas with osteoclast-like giant cells presenting cyto-histopathologic correlation: a case report J. Lages dos Santos*, A. Sanches, L. Santos *Centro Hospitalar de Vila Nova de Gaia / Espinho, Portugal Background & objectives: Among undifferentiated pancreatic car- cinomas undifferentiated carcinoma of the pancreas with accompa- nying osteoclast-like giant cells (UC-OGC) has been classified as an