Objectives: Except pancreatic adenocarcinoma, pancreatic cancer has several uncommon histological subtypes, including invasive intraductal papillary mucinous neoplasm (IPMN), pancreatic neuroendocrine tumor (pNET), adenosquamous carcinoma, invasive mucinous cystic neoplasm (MCN), acinar cell carcinoma (ACC), squamous cell carcinoma (SCC), and invasive solid pseudopapillary tumor (SPT). However, features of theses uncommon subtypes are not systematically analyzed.
Methods: Subjects with different histological subtypes of pancreatic cancers were retrieved from the Surveillance, Epidemiology, and End Results registry. Characteristics and behaviors of uncommon subtypes were compared.
Results: Pancreatic adenocarcinoma (85.8%) represented most primary pancreatic cancers, and other subtypes were rare (14.2%). Features of uncommon subtypes included females with SPT and MCN, located at the pancreatic body/tail of pNET, SPT, and MCN; poor differentiation of adenosquamous carcinoma and SCC; and large size of MCN, SPT, ACC, and SCC. In addition, IPMN, pNET, MCN, ACC, and SPT were indolent. For indolent subtypes, patients with locoregional tumor had prominent prognosis compared with patients with distant disease, especially for invasive IPMN (median survival, localized, 30.0 months; regional, 11.0 months; distant, 4.0 months).
Conclusions: The study systematically summarizes characteristics and behaviors of primary pancreatic cancer by histological subtypes, which can facilitate the management of pancreatic cancer.