Intraductal Tubular Adenoma of the Pancreas as a Possible Rare Variant of Gastric-type Intraductal Papillary Mucinous Neoplasm A Report of Two Cases

BACKGROUND: Intraductal tubular adenoma (ITA) of the pancreas has been reported recently, but no more than 20 cases have been documented. Two cases of ITA are described in order to investigate histogenesis and discuss the relationship between ITA and intraductal papillary mucinous neoplasm (IPMN). CASE: Two patients were hospitalized because of midsection discomfort and pancreatic mass. Both tumors presented as polypoid tumor in the cysts, located in the main pancreatic duct. Histologically they were composed of closely packed tubular glands or had a branching tubular growth pattern mimicking pyloric-type glands. The epithelia within the same cyst appeared typical of gastric IPMN. Pancreatic intraepithelial neoplasia (PanIN) IA and IB were present in smaller ducts around the tumors in both cases. The tumors predominantly showed neutral mucin. CK7 and MUC5AC stains were positive, whereas MUC1, MUC2, CK20 and CDX2 were negative; both of the IPMNs and associated PanINs shared the same immunohistochemical profile. The 2 patients had no recurrence of disease at 142 months and 38 months postoperatively, respectively. CONCLUSION: ITA is a rare, benign tumor almost always accompanied by gastric-type IPMN. It may be a variant of gastric-type IPMN. Smaller ducts around the tumor with low-grade PanIN are one of the features of the tumor. (Anal Quant Cytopathol Histopathol 2012;34:325-330)