ECP 2023 Abstracts

S198 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 E-PS-06-019 Digestive metastases of renal clear cell carcinoma: a series of three case reports and review of literature A. Cernat-Stefan*, R. Ardeleanu, M. Matanie, E. Ignat, M. Filip, A. Ciocan, S. Sabo, G. Micu, A. Bastian, S. Zurac *Colentina University Hospital, Romania Background & objectives: Clear cell renal cell carcinoma (CCRCC) is the most common type of renal cell carcinoma. 25–30% of patients already have metastatic disease on detection most likely due to minor clinical symptoms. Rare cases of digestive metastases (DM) have been reported. Methods: We searched the surgical pathology files of the Depart- ments of Pathology, Colentina University Hospital for cases of DM from CCRCC reported between November 2022 and March 2023. All Hematoxylin and Eosin (H&E) and immunohistochemical (IHC) stained slides were reviewed. Results: Three cases of DM were identified: a 58-year-old woman with gastric metastasis, a 60-year-old man with pancreatic metastases, and a 61-year-old man with cholecystic metastasis. Two of these patients had a record of primary CCRCC; the patient with cholecystic metastasis had no history of CCRCC. Gastric metastases presented endoscopically as gastric polyps. Pancreatic metastases were detected during a routine imaging check as intra-pancreatic nodular lesions, intensely iodophilic. Cholecystic metastasis had a cystic, polypoid ultrasound appearance. Histopathologically, the cases showed low-grade morphology polygo- nal cells with clear cytoplasm and slightly enlarged nuclei, with focal nucleoli visible at 100x magnification. The diagnosis was confirmed with immunostaining for PAX8 and CD10. Conclusion: Although DM from CCRCC are rare, the differential diag- nosis of clear cell proliferation in the gastrointestinal tract and pancreas should include CCRCC metastasis, especially in cases with history of primary renal tumour. Clinically, they might present as polypoid masses (especially gastric and cholecystic) or nodules. We presented three cases with low-grade morphology, whose main differential diag- noses were gastric xanthoma, cholecystic clear cell adenocarcinoma, and solid variant of pancreatic serous cystadenoma. PAX8 and CD10 immunostaining is useful in the differential diagnosis. E-PS-06-020 Gastric adenosquamous carcinoma - evaluation of clinicopathologi- cal prognostic factors E.E. Cetiner*, I.E. Cakir, A. Vergili, N. Ekinci *Izmir Katip Celebi University, Ataturk Training and Research Hospi- tal, Department of Pathology, Turkey Background & objectives: Gastric adenosquamous carcinoma is a rare entity that less than 0.25% of all gastric carcinomas. Prognosis is worse than conventional gastric adenocarcinomas. They usually diagnosed at late stage. For the diagnosis squamous component should be at least 25% of tumour. Methods: In this study, five cases diagnosed as adenosquamous carci- noma in 1875 gastrectomy operations between 2008-2022 were evalu- ated retrospectively. For all cases gender, age, tumour location, size, lymphovascular invasion, perineural invasion, pathological stage, prog- nosis and the type of metastases to lymph nodes were analysed. And those which originated from esophagogastric junction were excluded. Results: Adenosquamous carcinomas constituted 0,26% of all gas- trectomies. Among the five patients, the median age was 61,2(50-83), gender ratio was 2/3(M/F). Three tumours located distal stomach and two were proximal stomach. Median size was 6,34(3,5-10) cm. Lym- phovascular invasion has been observed on all tumours and four had perineural invasion. Pathological stage of three patients was pT4 and two was pT3. Also three patients were pN3, one patient was pN1 and one patient was pN0. Mean survival time is 13,4(1-26) months. As lymph node metastasis, adenocarcinoma component was dominant in two cases, squamous was dominant in one case, and both components were observed at a similar rate in one case. Conclusion: In conclusion, gastric adenosquamous carcinoma is a very rare tumour. Patients are usually diagnosed at late stage. The tumour has aggressive behaviour and poor prognosis. The pathogen- esis is unknown but there are several hypotheses in literature. The main prognostic factor is the stage at the time of diagnosis. Also the domi- nant component of the tumour is a prognostically important parameter. Since this entity is rare and aggressive, adequate prognostic data could not be provided. E-PS-06-021 A rare giant cell tumour in the gallbladder X.F. Chen*, M. Lee, K. Sittampalam *Department of Anatomical Pathology, Singapore General Hospital, Singapore Background & objectives: An elderly man who presented with acute cholecystitis was found to have a gallbladder tumour measuring 2.7cm on computed tomography scan. The imaging finding was suspicious for a neoplasm. He subsequently underwent a radical cholecystectomy with liver segment 4b/5 resection. Methods: The gross examination of the gallbladder showed a cir- cumscribed, exophytic tumour arising from the submucosa with a tan haemorrhagic appearance. Representative sections of the tumour were submitted for microscopic examination. Results: Histological examination of the tumour showed epithelioid to spindled mononuclear cells interspersed with many osteoclast-like multinucleated giant cells. Areas of infarction, haemorrhagic cystic degeneration, haemosiderin deposition, and osteoid-like material were observed. Scattered mitoses were seen. No epithelial dysplasia of the lining gallbladder epithelium or marked nuclear pleomorphism of the lesional cells was present. By immunohistochemistry, the lesional mononuclear cells were positive for CD163, CD68 and P63, whilst being negative for EMA, MNF116, clusterin and H3.3G34W. The multinucleated giant cells were positive for CD68. Ki67 proliferation index was 10% to 15%. The features were in keeping with a giant cell tumour despite the unusual location. Conclusion: Herein, we reported a rare case of giant cell tumour in the gallbladder. The main differential diagnosis was an undifferenti- ated carcinoma with osteoclast-like giant cells. In this case, there was no marked cytological atypia, area resembling conventional carci- noma or epithelial differentiation of the lesional cells immunohisto- chemically to support the diagnosis of an undifferentiated carcinoma or malignancy. To our knowledge, there were only two reported cases of giant cell tumours in the gallbladder, and both pursued benign courses. E-PS-06-023 Clear cell change in colorectal epithelial neoplasms: two case reports S.K. Dursun*, H. Karatay, N. Dursun Kepkep *Basaksehir Cam and Sakura City Hospital, Turkey Background & objectives: Clear cell change in colorectal epithelial neoplasms is rarely encountered. The pathogenesis of these lesions remains unclear. It is unclarified whether it is caused by a cytoplasmic accumulation of glycogen or lipid-like material. Methods: We report two colorectal neoplasms with clear cell change. Case 1: 57-year-old male who presented with a 3 cm pedunculated rectal polyp in colonoscopy and the polyp was excised. Case 2: 74-year-old female who presented with bowel obstruction and urgent surgery was decided. During operation, an ileocecal tumoral mass was detected and right hemicolectomy was performed. Results: Histological examinations of materials: