Intraductal Tubular Carcinoma of the Pancreas: Differential Diagnosis and Distinction From Intraductal Tubular Adenoma

Abstract

We describe a representative case of intraductal tubular carcinoma (ITC) of the pancreas, with particular emphasis on its differential diagnosis and morphologic features. Macroscopically, ITC shows nodular growth without mucus secretion and is confined within the main pancreatic duct. Histologically, ITC consists mainly of tubular glands in a back-to-back arrangement without evidence of multistep progression. The cuboidal cells are uniform. Pathologists face the challenge of distinguishing ITC from the intraductal tubular variant of acinar cell carcinoma, pancreatobiliary-type intraductal papillary mucinous carcinoma, and intraductal tubular adenoma (ITA). Histochemistry for mucins 1, 2, 5AC, and 6 and immunohistochemistry for trypsin can be helpful in distinguishing ITC from other intraductal neoplasms. The ITC in our case shows no K-ras exon 12 or 13 mutation, indicating that the lesion differs from ordinary intraductal papillary mucinous carcinoma. With a lining of columnar cells, the tubules of ITA resemble pyloric glands seen in the stomach. Together with the confirmed absence of mucin 5AC expression in our case, the present review indicates that ITC is not biologically associated with ITA, and ITA should be considered a phenotypic variant of intraductal papillary mucinous neoplasm.