The adrenal medulla occupies the central portion of the adrenal gland and accounts for about 10% of total adrenal gland volume.

Clearer understanding of the cellular mechanisms involved in the secretory characteristics of pheochromocytomas and sympathetic paragangliomas may offer one approach for the discovery of novel prognostic biomarkers for improved therapeutic targeting and monitoring of treatment or disease progression. Therefore, there is an unmet need for prognostic biomarkers. Histopathological examination currently poorly predicts future biologic behavior, thus long term postoperative follow-up is required. Pheochromocytomas and paragangliomas are usually locally confined tumors, but about 15% do metastasize to distant locations. Chromaffin cell tumors also include sympathetic paragangliomas originating in sympathetic ganglia. This uncontrolled secretion can be partly explained by perturbations of the molecular catecholamine secretory machinery in pheochromocytoma cells. Pheochromocytomas are adrenomedullary tumors that are characterized by uncontrolled synthesis and secretion of catecholamines. In this review, we provide a detailed description of the route from stimulus to secretion of catecholamines by the normal adrenal chromaffin cell compared to chromaffin tumor cells in pheochromocytomas. The pathways involved have been extensively studied, and various elements of the underlying molecular machinery have been identified.

Catecholamine biosynthesis and secretion is a complex and tightly controlled physiologic process. The adrenal medulla is composed predominantly of chromaffin cells producing and secreting the catecholamines dopamine, norepinephrine, and epinephrine.

Catecholamines adrenal medulla