ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 which were confirmed by immunohistochemistry. The rest of the pancreas showed multifocal low grade pancreatic intraepithelial neoplasia (PaIN) Conclusion: Presence of Leydig cells in the ovarian-type stroma of MCN has not been widely reported. This finding suggests that the ‘ovarian-type’ stroma may in fact actually be ovarian stroma, which further supports the theorized pathogenesis of this tumour, that the ectopic ovarian stroma incorporated in the pancreas during embryogenesis may become activated in the setting of hormonal imbalance. Presence of multifocal PaIN in the case also support possible common mutations and genetic pathway. E-PS-07-007 Caveolin-1 and p21 induction in aggressive pancreatic neuroen- docrine neoplasms E. Koniaris*, A. Kataki, I. Angelioudaki, L. Stoupis, A. Mitrousias, A. Tzingounis, G. Zografos, M.M. Konstadoulakis, G. Kafiri *Pathology department, General hospital of Athens "Hippokratio", Greece Background & objectives: Research data denotes Pancreatic Neuroen- docrine Neoplasms (pNENs) to represent genetically different entities, tumours (pNETs) and carcinomas (pNECs) with different malignant potential. Current study explores senescence associated marker p21 and senescence regulator Caveolin-1 expression profiles between the two subtypes. Methods: Both protein expression profiles were studied immu- nohistochemically in paraffin-embedded pancreatic lesions and normal adjacent tissues (NAT) from 24 pNEN patients (13 pNETs and 11 pNECs mean-age: 59.69±3.2 and 61.18±3.2 respectively). Staining intensity scores were calculated by multiplying intensity (negative to high: 0-3) with the immunoreactive score: 0-10%=1, 11-50%=2, 51-80%=3, 81-100%=4) and data were statistically analysed using SPSS 26. Results: Immunostaining of senescence marker p21 was increased in both cancer epithelium and stroma (pNEC) com- pared to NAT corresponding elements (p=0.048 and p=0.04 respectively). Induced p21 expression was also detected in pNEC patients both epithelium and stroma when compared to pNET patients (p=0.002 and p=0.024 respectively). In between pNEN groups caveolin-1 expression was also more prominent in pNEC patients’ epithelium. Still within pNEC patient group loss of caveolin-1 expression in their epithelium was observed in those with positive lymph nodes metastasis (p=0.034). In the pNET a reduction in the expression of caveolin-1 was observed in the presence of inflammation (p=0.03). Conclusion: Based on p21 expression, induced senescence seems a common feature of pNENs although more prominent in pNECs and with caveolin-1 concomitant expression in pNEC epithelium to promote senescence. A role of caveolin-1 protein in tumour pro- gression was also apparent, as loss of expression in pNECs epi- thelium with high metastatic potential was observed. Additionally, loss of stromal caveolin-1 upon the presence of inflammation in pNETs was observed potentially associated with caveolin-1 medi- ated senescence due to release of SASP factors. E-PS-07-008 Mucoepidermoid carcinoma of the liver: a rare, diagnostically challenging case A.H. Aydin*, S. Yamak, G. Gürsoy, İ. Ovali Erdoğdu, Y.B. Özoğul *Ankara City Hospital, Turkey Background & objectives: Mucoepidermoid carcinoma (MEC) is a malignant epithelial neoplasm that arises most common in major sali- vary glands. It occurs rarely in liver. To now there have been less than 20 cases reported. We report a case of primary MEC of liver. Methods: Our patient was a 70-year-old female. A mass of approximately 65x55 mm in size, located in the liver segment 5 was detected. It was evaluated as a possible primary liver malig- nancy. Then the patient was taken liver segmentectomy operation. In macroscopic examination an ill-defined lesion was detected. Results: Histology of the lesion revealed that the tumour was composed of tumour cells that coalescing as glandular structures and solid nests in some areas as well. On non-cirrhotic background there was a tumour that consisted of the mixture of squamous, mucinous and intermediate cells to varying degrees. Histomorphologic and immunohistomorfologic evidence were interpreted as mucoepidermoid carcinoma. Any possible primary focus was not detected by additional imaging methods, so the tumour was diagnosed as MEC which is an uncommon subtype of intrahepatic cholangiocarcinoma. Conclusion: MEC is the most common malignant epithelial neo- plasm of salivary glands in adults and children. It rarely occurs in other organs. MEC of the liver is extremely rare. First case in liver was presented by Pianzola and Drut in 1971. Due to its rela- tive infrequency in liver, the pathogenesis has not been elucidated. Primary MEC of the liver is a highly aggressive tumour with the overall survival shorter than 6 months. E-PS-07-009 Solid pseudopapillary neoplasms of the pancreas, a study of 4 cases S. Kartal*, E. Tuncer, H. Özer *Sivas Cumhuriyet University, Turkey Background & objectives: Solid Pseudopapillary Neooplasms (SPNP) of the pancreas are rare and low grade pancreatic neoplasms, seems dominantly in females. We aimed to evaluate retrospective data analy- sis, clinical, macroscopic and microscopic features of our SPNP cases and compare them with the literature. Methods: Here we presented four cases of SPNP which were diag- nosed between 2012-2022 years in Sivas Cumhuriyet University Pathology Department. We reassessed our cases and compared our findings with the literature. Results: All the patients were female. Their ages ranged from 18 to 58 years with an average of 42. The tumours were located in various parts of the pancreas and the average size was 5 cm. Macro- scopically, all lesions had shown cystic and solid areas. The young- est patient had a history of pituitary adenoma and suspicion of Lynch syndrome due to PMS-1 heterozygosity. None of the patients had metastatic lesion. Microscopically none had lymphatic inva- sion and two patients were assessed as pT3 due to peripancreatic adipose tissue invasion. All of the SPNP cases had heterogene- ous pattern with solid and pseudopapillary structures and showed haemorrhagic and pseudocystic changes in various areas. Conclusion: When the clinical, microscopic and macroscopic fea- tures of our cases were evaluated, they were found to be compatible with the literature. In addition, although a few cases of other pan- creatic tumours incidentally associated with Familial Adenomatous Polyposis Syndrome have been reported in the literature, there is no definite data about the association of pancreatic tumours with Lynch syndrome as probably suspected in one of our cases. Addi- tional studies are needed to elucidate this issue. E-PS-07-010 S241