Abstract: Objective:To explore the clinicopathologic features and differential diagnosis of pancreatic endocrine tumor(PET).Methods:The clinicopathologic and immunohistochemical features of 3 PET were analysed.Combined with the literatures,the diagnosis of pancreatic acinar cell carcinoma were identified.Results:The PET cells were solid flake and trabecular shape,acinar-like arrangement and not significant cellular atypia,and rich blood vessels in intercellular substance.Chromogranin A,synaptophysin,and the endocrine markers of insulin were detected by immunohistochemistry.Conclusions:Most PET are benign,but the pancreatic acinar cell carcinoma is highly invasive tumor.The morphology of the pancreatic acinar cell carcinoma is similar to the PET,and the biological behaviors of two types tumor have significantly different,and distinguishing two types of famor has obvious clinical significance.