Ductuloinsular tumors of the pancreas: a light, electron microscopic and immunohistochemical study.

Most pancreatic tumors are of a single cell type and are identified delta as duct, acinar, or islet cell neoplasms. The authors report on three examples with both duct and endocrine characteristics as seen by light microscopy; two with further confirmation of endocrine differentiation by electron microscopy; and one by immunocytochemistry. Mixed differentiation of this sort can be understood by reference to the embryonic pancreas, which develops from the small intestine and forms ducts, intercalated ducts, acini, and islets, with their different cell types. The merging and intermingling of different cell prevents the identification of one specific cell of origin. It also suggests that the neoplastic process here may not be a clonal proliferation from a single cell mutation as this is generally understood. Alternative explanations are briefly mentioned.