Abstract
During the cytochemical investigation of human parotid mixed tumors, focal alkaline phosphatase activity was observed along the nuclear envelope of many neoplastic epithelial cells. Further investigation localized the enzyme reaction product within the nuclear pore and in relation to the pore-associated material. Commonly, the reaction product assumed a geometric pattern and measurements of the reaction product deposits (761 ± 8 Å) conformed to the size of the nuclear pore. The possible significance of the presence of the enzyme in the nuclear pore is discussed.