SYP and cholangiocarcinoma: 2) electron microscopic confirmation of secretory zymogen granules 3) immunohistochemistry demonstrating negative staining for liver cell types or HCC (negative HepPar1), for bile duct epithelium or cholangiocarcinoma (negative cytokeratin 19), or neuroendocrine tumour (negative Chromogranin and Synaptophysin).