Ultrastructural features of functioning alpha- and beta-cell tumors

Alpha-cell neoplasms associated with hyperacidity and the Zollinger-Ellison syndrome and beta-cell neoplasms presenting with hypoglycemia were studied by electron microscopy. The severity of the clinical manifestations covered a broad range. The ultrastructural morphology of tumors within the same group varied considerably. Most conspicuous was the presence of abundant, mature, specific granules in cells from tumors associated with mild clinical syndromes. Conversely, cells from tumors presenting with the most severe symptomatology displayed few and immature-looking granules. It is suggested that an alteration in the secretory mechanism of neoplastic alpha and beta cells may result in the production of substances structurally different from the secretory material of their nonneoplastic counterparts. These abnormal granules would have a similar or possibly even enhanced hormonal potency while their structural differences could explain their his-tochemical negativity.