The two patterns of pathogenesis for pancreatic colloid carcinoma are reported; (1) progression from ordinary ductal adenocarcinoma, a subtype of invasive pancreatic ductal carcinoma, and (2) progression from papillary adenocarcinoma derived from intraductal papillary mucinous neoplasm (IPMN) or mucinous cystic neoplasm (MCN). Whether these two conditions are the same disease remains controversial. Case Report 1. An 81-year-old woman was evaluated for an increased carbohydrate antigen 19-9 (CA19-9) value (130 U/mL) detected at 4-year follow-up after distal pancreatectomy for IPMN. Based on the image findings, a local recurrence of IPMN was diagnosed, and the patient underwent a remnant total pancreatectomy. Histopathologic findings showed marked mucus production from the tumor, also noteworthy because mucous nodule formation occurs in more than 80% of tumor. Fibrosis around the mucous cavity was noted, and a low papillary lesion was found in part of the cyst wall, which was contiguous to a flat, basal area; its nucleus was enlarged and heterogeneous in size, which is considered to be a component of intraductal papillary mucinous (IPMC). Therefore, the patient was diagnosed with pancreatic colloid carcinoma derived from IPMN. Case report 2 a 71-year-old man was evaluated for jaundice. Based on the image findings, a diagnosis of pancreatic head cancer was made, and a substomach preserving pancreaticoduodenectomy was performed. Histologically, marked mucus production and floating cuboidal masses of atypical cells without mucinous nodules were seen. Mucinous nodule formation is observed in more than 80% of tumor, but there was no IPMN component, which led to the diagnosis of pancreatic colloid carcinoma. In conclusion, there might be two types of colloid carcinoma of the pancreas, and further study is needed to determine whether these diseases are truly the same or not.
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