ECP 2023 Abstracts

S231 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 had a history of a 4-month dull (vague) epigastric pain and one episode of acute right-upper-quadrant abdominal pain. The gallbladder was radiolog- ically unremarkable. The patient underwent liver biopsy, liver segments IVB/V/VI excision, en block with gallbladder and right nephrectomy. Results: Liver biopsy was diagnostic of large cell neuroendocrine car- cinoma (LCNC). Renal biopsy showed a Fuhrman 2, clear cell RCC. Following removal of tumours, the liver tumour mass was 8,5X7X6cm in size, centrally necrotic and was in continuity with the gallbladder. Gall- bladder was 6,5X2,8X2cm, had a hard consistency in the neck area, where a 2-cm intramural gallstone was found. The mucosa was unremarkable. After fixation, there was eccentric wall thickening of 5,5X1cm, in juxta- position with the liver mass, in liver segment V. Histologic examination revealed infiltration of the gallbladder wall by LCNC cells, admixed with pleomorphic adenocarcinoma cells, with variable areas of dysplastic epi- thelium in association with reactive mucosal lymphoid follicles. Conclusion: Neuroendocrine neoplasms of the liver are metastatic from other organs. GB-MANEC is an extremely rare neoplasm, occur- ring in middle-aged females, incidentally found at cholecystectomy specimens. The most common symptom is vague abdominal pain and is usually associated with cholelithiasis. There are no specific symptoms and image findings. In LCNECs of the liver, in patients with symp- toms or signs resembling cholecystitis, the suspicion of GB-MANEC, extending to the liver, should be raised. Simultaneous occurrence of RCC has not been described before. E-PS-07-048 Schwannomatosis in periampullary duodenum and peripancreatic tissue mimicking malignancy, challenging case report B. Yeni Erdem*, N. Berker, G. Unverengil, K.R. Serin, M. Buyuk *Kartal City Hospital, Department of Pathology, Turkey Background & objectives: Schwannomatosis is a rare disorder char- acterized by multiple noncutaneous, nonvestibular schwannomas, which typically affect the peripheral or spinal nerves in the absence of neurofibromatosis. Visceral involvement is infrequent. Diagnosis can be made through clinical or combined molecular and clinical criteria. Methods: Herein, we present a case of schwannomatosis with periampul- lary and peripancreatic localizations, clinically mimicking malignancy in a 38-year-old male patient who presented with right upper quadrant pain. Results: Computer tomography displayed multiple masses between the duodenum and jejunum. Upper endoscopy revealed a mass in duode- num, and the biopsy revealed spindle cell proliferation which showed diffuse S100 expression consistent with schwannoma. A pylorus-spar- ing pancreaticoduodenectomy was performed. Macroscopic examina- tion revealed three separate tumoral masses in periampullary region (3.5 cm), peripancreatic tissue (3.5 cm), and mesentery of duodenum (6 cm). Tumours were nodular-shaped and multilobulated. Microscopi- cally, tumours consisted of spindle cells arranged in fascicles alternat- ing between cellular and loose-myxoid areas. No necrosis, mitosis, or atypia was observed. The tumour cells showed strong immunoreactivity with S100 and NSE. Immunostains for CD117, DOG1, and CD34 were negative. We rendered the diagnosis as schwannomatosis. Conclusion: Approximately one-third of cases have anatomically local- ized disease with tumours limited to one side or segment, as in our case. This is defined as segmental schwannomatosis. In our case, the nodules were separate but were in close proximity. No vestibular schwannoma was detected on radiologic imaging, and our case fulfilled the clinical criteria of schwannomatosis. Neither he nor his relatives had a proven genetic syndrome. Although the disease is usually sporadic, genetic tests should be preferred to detect familial cases. E-PS-07-049 Adult pancreatoblastoma (PB): report of a rare and challenging case diagnosed on core needle biopsy (CNB) S. Zanella*, S. Uccella *Department of Biomedical Sciences, Humanitas University, Milan, Italy, Pathology Service, IRCCS Humanitas Research Hospital, Milan, Italy Background & objectives: PB is a malignant neoplasm of the pan- creas, representing 25% of paediatric pancreatic. Only about 40 cases of adult PB have been reported. We present an additional case diag- nosed on CNB thanks to the employment of a selected immunohisto- chemical panel. Methods: A 53-year-old man presented with deep abdominal pain and jaundice. A CT scan showed a 15 cm retroperitoneal mass of question- able pancreatic origin. A CNB was performed. Microscopically, a largely necrotic proliferation of epithelial cells with large eosinophilic cytoplasm and round nucleoli with finely dispersed chromatin. An immunohisto- chemical panel including cytokeratins, transcription factors, acinar and neuroendocrine markers, and cancerogenesis-related markers. Results: Immunohistochemistry was positive for CK-pool, CK19 (focal), synaptophysin, Bcl10 (focal), trypsin (focal), AFP (focal). Negative markers were chromogranin A, Islet1, TTF1, PAX8, OCT4, p63, CDX2, arginase, HepPar, NKX2.2. p53 and Rb were normally expressed; a misplaced nuclear beta-catenin staining was found. These findings were consistent with a pancreatic neoplasm with acinar and neuroendocrine differentiation. Despite typical squamoid nests were not visible, the positivity for AFP and the altered expression of beta-catenin suggested the diagnosis of PB. The revision of CT images confirmed the pancreatic pertinence of the lesion and a duodenocephalopancreatec- tomy was performed. On the surgical specimen, the typical morphology of PB was present. Three hepatic metastases were also resected. Conclusion: Adult PB is histologically characterized by prolifera- tion of epithelial cells with acinar and neuroendocrine differentiation and presence of squamoid nests. AFP expression and alteration of the APC/beta-catenin pathway are frequently present. Diagnosis on small biopsy samples is difficult, the main differential diagnoses being acinar cell carcinoma and neuroendocrine neoplasms. Recognition of a suggestive morphology and application of immunohistochemical panel including neuroendocrine and acinar markers, AFP and beta- catenin are crucial in achieving the diagnosis, prompting a correct patient management. E-PS-08 | E-Posters Digital and Computational Pathology E-PS-08-001 Improving PD-L1 quality control using a dynamic range cell line and Qualitopix analysis N. ’t Hart*, L. Gal, M. Grønning Nielsen, H. Høeg *Isala, The Netherlands Background & objectives: Immunohistochemistry (IHC) with PD-L1 is in use to predict ICI response in NSCLC patients. Inter-observer, inter- and intra-laboratory variability is, however, a known issue. To improve consistent scoring of PD-L1, IHC quality control is essential before applying artificial intelligence (AI). Methods: To define variability of PD-L1 (1:50 22C3 laboratory developed test (LDT)) a dynamic range cell line (HistoCyte, NewCas- tle, UK) is repeatedly stained. Staining results were quantified using intensity scores (Qualitopix, Visiopharm, Hørsholm, DK). To illustrate relevance of a dynamic range control, alterations to the staining proto- col were introduced for a NSCLC-TMA. Mean, SD and coefficient of variance (CV) were calculated. Results: Quantification of PD-L1 expression in the cell line (n=100) showed: negative 0.00% ± 0.00 (mean ± SD), weak 9.04% ± 7.69, intermediate 96.01% ± 4.95 and strong positive 99.30% ± 0.91 cores. The CV was high in weak (85.01%) and intermediate (5.16%) cores, while it was low in negative (0.00%) and strong positive (0.92%) cores.