Pancreatic neuroendocrine tumors of the main pancreatic duct are rare and usually small due to symptoms of pancreatic duct obstruction. We present a case of a large (3 cm), well-differentiated (G1) lipid-rich polypoid neuroendocrine tumor of the pancreas completely occluding the main pancreatic duct with non-neoplastic-entrapped ductules and CK19 positivity. Clinical, radiological, gross, microscopic, immunohistochemical, and ultrastructural findings are discussed. The literature pertaining to the unique features of this case is reviewed including clinical and pathologic pitfalls and the possible etiologic and prognostic significance of these findings.