[APUD cells and apudomas].

Synthesis of biologically active amines and peptides, and accumulation of them in the cytoplasm in the form of secretory granules of "neuroendocrine" type are among the most important characteristics of APUD cells. Apudomas, tumors consisting of cells with the properties of APUD elements, have many common morphological and functional features, although they are quite heterogeneous by clinical behavior and histogenesis. Histological diagnosis of apudomas requires the assessment of the endocrine function of the tumor cells for which histochemical and electron microscopic methods must be employed, as well as consideration of the clinical and biochemical indices of the hormonal activity of the tumors.