An endocrine organ benign neoplasm that arises within the adrenal medulla, releasing epinephrines and norepinephrines hormones that cause either episodic or persistent high blood pressure. [ http://purl.obolibrary.org/obo/ECO_0007637 http://purl.obolibrary.org/obo/ECO_0007638 http://purl.obolibrary.org/obo/ECO_0007636 ]