ECP 2023 Abstracts

S229 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 14 appendiceal, 4 gastric, 4 duodenal, 1 ampullary and 4 colorectal tumours. Representative tissue sections were stained for PD-L1 (clone 22C3, DAKO) using the Ventana Benchmark platform. PD-L1 expres- sion was determined using the combined positive score (CPS). Results: Cases were classified according to their morphology and graded using Ki-67 expression as follows: 41 NET G1, 27 NET G2, 1 NET G3 and 3 NEC. Out of 74 cases, 57 had <1 CPS and were considered negative, and 2 cases originating from the appendix were not classified due to major inflammation caused by acute appendicitis. In positive cases, PD-L1 CPS mean value was significantly higher in NECs compared to NET G2 and NET G1 tumours (p<0.0001, 9.66 vs 2.33 and 1.33, respectively). The only NET G3 case included was negative. Correlation analysis revealed no associations between PD-L1 CPS and location, stage, lymph-node metastasis, lympho-vascular or perineural invasion. Conclusion: This study shows that higher PD-L1 CPS values are found in NECs, possibly supporting immunotherapy as a promising future therapeutic strategy. PD-L1 expression in NET G3 cases should be investigated further in larger cohorts. Funding: Vladimir Totovici Research Grant - Project number: T0476/41987/2022/kg E-PS-07-041 Survivin expression as a potential prognostic marker in gastro- entero-pancreatic neuroendocrine neoplasms A.D. Plopeanu*, A. Yavas, L. Haeberle, I. Esposito *Anapatmol Research Center, Victor Babes University of Medicine and Pharmacy, Romania Background & objectives: Gastro-entero-pancreatic neuroendocrine neoplasms (GEP-NENs) are malignancies with variable clinical behav- iour and have few therapeutic options. We explored Survivin (BIRC5) expression, an apoptosis inhibitor protein, as a potential prognostic marker in a large collective of GEP-NENs. Methods: 64 GEP-NENs diagnosed between 2015 and 2022 were included. The database consisted of 24 pancreatic (3 liver metasta- sis), 19 ileal, 6 appendiceal, 5 gastric, 2 duodenal and 7 colorectal cases. Representative tissue sections were stained for Survivin and both nuclear and cytoplasmic expression were evaluated using the IRS score. Results: Cases were classified according to morphology and graded using Ki-67 expression as follows: 33 NET G1, 19 NET G2, 4 NET G3 and 8 NEC. Survivin expression was considered positive if IRS value was ≥2. NET G3 and NECs had higher cytoplasmic IRS compared to NET G1 and NET G2 (p=0.0007, 6.5 and 3.8 vs 2.45 and 3.57, respec- tively). NET G1 cases showed no nuclear positivity, only 2 NET G2 cases had nuclear positivity and were both diagnosed in early stages. 3 NET G3 and 5 NEC cases showed nuclear Survivin expression. Out of 5 resection cases with nuclear Survivin expression, 3 presented lymph- node metastasis and 4 presented distant metastasis. Conclusion: Higher cytoplasmic and nuclear Suvivin expression was directly correlated with a higher tumour grade and a more aggressive clini- cal behaviour in NET G3 and in NECs compared to NET G1 and NET G2 tumours. These results support the usefulness of Survivin as a prognostic marker in GEP-NEN and need to be confirmed in larger collectives. Funding: Vladimir Totovici Research Grant - Project number: T0476/41987/2022/kg E-PS-07-042 Epstein Barr Virus-associated post-transplant smooth muscle tumours (EBV-PTSMT) of uncertain behaviour. A short series including hepatic and multicentric tumours with literature review Y. Rodriguez*, A. Illarramendi, A. Luzmila-Vasquez, E. Revilla, F. Cambra, C. Barcena *Hospital Univ 12 de Octubre, Spain Background & objectives: EBV-associated PTSMT are very rare tumours related to immunosuppression. Less than 80 cases have been reported up to this moment, and more knowledge is needed. We describe the clinico-morphological features of 2 new cases of EBV- PTSMT and literature review. Methods: We gathered two cases of female adults. First case, was a cystic fibrosis patient who received lung transplant (LT) and second case a membranous glomerulonephritis kidney transplant (KT) recipi- ent. In both patients ultrasound study showed hepatic incidental masses that were confirmed with CT scan, the patient with LT presented pre- vious colonic exophytic lesions. We performed morphological and immunohistochemical study. Results: CASE 1: LT woman 48 years-old presented 3 years after transplant, 2 ulcerated lesions in right colon and 5 incidental liver nodules. There have not been other lesions after 3 months. CASE 2: KT woman was 44-years-old woman, transplanted 10 years before. Presented an incidental liver mass 4,3 cm size. Surgical treat- ment was performed with no recurrence 4 years later. Both liver lesions were compound of interlacing fascicles of moder- ately differentiated spindled cells, with mixoid areas and others with high cellular density. Mitotic rate was high in inmature areas of both tumours (6-9/ 10 hpf). EBV-positive (in situ hybridization). Colonic lesions were well differentiated EBV-SMT with low mitotic activity. Conclusion: EBV-SMT is a poorly understood entity with uncertain biological behaviour. We hypothesize that persistently high EBV viral loads, could be a risk factor for post-transplant EBV-SMT as the mul- ticentric case was IgM seropositive with peripheral blood positive viral load. Both cases had sarcomatous features with high cellular density and mitosis but they were not related to recurrence. Literature review shows a better prognosis than conventional leiomyosarcoma. It is important to test EBV in all mesenchymal tumours arising in immu- nocompromised patients. Funding: We received a grant from FUNDATION MUTUA MADRILEÑA to study liver tumours E-PS-07-043 Unusual localisation of plasmacytoma: pancreatic presentation Z. Sağnak Yılmaz*, I. Saygin, S. Aydin Mungan, Z. Turkmen Usta *Dokuz Eylül University, The Institute of Health Sciences, Department of Molecular Pathology, Karadeniz Technical University, Faculty of Medicine, Department of Pathology, Turkey Background & objectives: Plasmacytoma is a solitary tumour which consist of atypical plasma cells. It can be primary as solitary mass without bone marrow involvement or may accompany multiple myeloma. Involvement of the pancreas was reported in only 2.3% of autopsies. Methods: The surgical specimens were formalin-fixed and paraffin embedded. The section were stained with routinary H&E. Results: A 79-year-old male patient who was followed up with a diag- nosis of low-grade B-cell lymphoma, a mass in pancreas was detected on computed tomography scans. The mass was 70 x 66 mm in diameter in the neck of the pancreas and surrounds the splenic artery. In addi- tion, solid nodules (metastases?) are seen at the level of the ribs. Micro- scopically, atypical plasma cells which have an eccentrically located nucleus were seen in the pancreatic parenchyma. CD38 and CD138 were positive in the immunohistochemical study. Immunoreactivity of Trypsin was weak. However, they were negative for panCK. Ki-67 proliferation index was 80%. Conclusion: Extramedullary plasmacytomas are mostly found in the upper respiratory tract. Pancreatic involvement is rare. In case of patients with multiple myeloma and focal or diffuse enlargement of the pancreas, plasmacytoma should be kept in mind for the differential diagnosis. Unlike pancreatic adenocarcinomas, surgical procedures are not commonly performed due to the systemic nature of the disease and