Ultrastructure of Multiple Pancreatic Tumors in a Case of Zollinger-Ellison Syndrome

Simultaneous occurrence of two differently structured islet cell tumors associated with nesidioblastosis in a woman affected by a Zollinger-Ellison syndrome is described. In Tumor I the ultrastructure of the cell granules, which have a dense core surrounded by an empty halo delimited by a membrane, and the lack of the metachromasia and argyrophilia suggests that the cells are of the alpha type. Histologically, the arrangement of the cells in cords and rows, the abundant fibrous stroma, the pleomorphism and atypism, and the richness of newly formed ducts seem to reveal a lesser degree of endocrine differentiation. Tumor II and adenomas have the same sinusoidal ribbon pattern. The morphology of the cell secretory granules, which are small and with a strictly apposed membrane, the metachromasia, and argyrophilia, suggest that the cells may be of the delta type. The uncertainty in the identification and correlation of alpha and delta cells in normal islets and in tumors does not allow any definite conclusions.