A Rare Tumor in Adulthood: Extrapancreatic Pancreatoblastoma.

Pancreatoblastoma is a rare malignant epithelial neoplasm of the pancreas. It primarily occurs in the pediatric population and is extremely uncommon in adults. A 64-year-old male patient with no known systemic disease presented to our clinic with abdominal pain and dyspeptic complaints. On physical examination, a tender epigastric mass was palpated. The patient was operated on with a preliminary diagnosis of gastrointestinal stromal tumor. Enbloc resection of the mass was performed. The transverse colon was segmentally resected with wedge resection of the gastric corpus. A stapled side-to-side anastomosis was performed. The macroscopic examination of the case revealed a tumoral lesion of approximately 16x13.5x10m, located in the submucosal area between the gastric corpus and the transverse colon. The microscopic examination showed acini, which have a highly cellular appearance, contain areas of necrosis, and form nested structures in places, stratification in places. The immunohistochemical examination demonstrated positive Trypsin expression, while focal positive expression of neuroendocrine markers such as Synaptophysin, Chromogranin, and Insulinomaassociated protein 1 (INSM-1) was observed. In betacatenin staining, aberrant nuclear and cytoplasmic positive expression was observed, and this staining pattern and morphology confirmed the diagnosis of pancreatoblastoma. Pathological Stage:pT3,N0,Mx the patient had an uneventful postoperative period and was referred to the oncology department for adjuvant chemotherapy. Pancreatoblastoma is an extremely rare type of pancreatic cancer and there are no established guidelines for the treatment of this aggressive disease. Surgical resection is recommended if anatomically possible. Pancreatoblastoma should be considered in the differential diagnosis of asymptomatic masses containing cystic-solid components and reaching very large sizes. Key words: Pancreas,Rare tumor, Pancreatoblastoma.