Contributor: Gordon K. Klintworth
Several different types of carcinoma arise in the pancreas. Premalignant lesions in the pancreas are pancreatic intraepithelial neoplasia and intraductal papillary mucinous neoplasms. Intraductal papillary mucinous neoplasms may be associated with an invasive ductal adenocarcinoma or colloid carcinoma. 
The vast majority are carcinomas of  the pancreas are ductal adenocarcinomas [adenocarcinoma - ductal], which has an overall 5-year survival rate of <5% and which arise from the pancreatic duct [carcinoma - pancreatic duct]. With surgical resection the 5-year survival rate is <15%. They arise from a pancreatic intraepithelial neoplasia or an intraductal papillary mucinous neoplasm. 
Colloid carcinoma [carcinoma - colloid] of the pancreas has an indolent course and the 5-year survival following resection, even in the presence of  lymph node metastases is 55%.
Carcinomas of the pancreas can spread by the lymphatic vessels to the regional lymph nodes. They can also spread by a perineural invasion. Distant metastases can reach distant sites including the uvea and orbit [carcinoma - metastatic].
Carcinoma of the pancreas is relatively common malignant neoplasm, It accounts for ~25,000 deaths per year in the USA. The prognosis is poorly partly because the tumor is usually not diagnosed until after local invasion or metastatic spread. Different types of carcinoma can arise in the pancreas. They include ductal carcinoma, adenosquamous carcinoma, mucinous noncystic carcinoma, signet ring cell carcinoma, undifferentiated (anaplastic) carcinoma, small cell carcinoma [carcinoma - small cell], mixed ductal endocrine carcinoma, serous cystadenocarcinoma, mucinous cystadenocarcinoma, intraductal papillary-mucinous carcinoma, acinar cell carcinoma, acinar cell cystadenocarcinoma, solid-pseudopaillary carcinoma and miscellaneous other types of carcinoma. A mucoepidermoid carcinoma can also arise in the pancreas.
The ductal adenocarcinoma accounts for 80-90% of pancreatic carcinomas. Cigarette smoking is an established risk factor. 75% of human pancreatic carcinomas have an activated c-K-ras oncogene usually with a mutation in codon 12. About 50% of pancreatic carcinomas have lost the normal p53 protein. Adenocarcinoma of the pancreas may be difficult to differentiate from chronic pancreatitis. Pancreatic carcinoma usually first spreads by the lymphatics to the regional lymph nodes. It also metastasizes to the peritoneum, liver, lungs and pleura. Hemmatogenous spread to the eye and ocular adnexa can occur. Pancreatic carcinoma especially in the head of the pancreas is often associated with diabetes mellitus, probably as a consequence of an impaired insulin secretion due to an obstructive pancreatitis.