Introduction
The parasympathetic nervous system is the site of origin of paragangliomas (PGLs) localized in the head and neck region. These head and neck PGLs are usually benign and hormonally inactive.1
PGLs have been referred to as chemodectomas and non-chromaffin lumors. Currently they are named by anatomic site: carotid PGL, tympanic PGL, jugular PGL, and vagal PGL. Other PGLs at less common sites are laryngeal PGL, orbital PGL, and aorto-pulmonary PGL. Approximately 1 of every 30,000 head and neck tumors is a PGL.2
Mast PGLs present clinically as solitary lesions. However, they can also be multifocal. PGLs may also be components of syndromes such as multiple endocrine neoplasia type 2, von Hippel-Lindau disease, and neurofibromatosis type 1. A familial basis of these tumors has been firmly established, with identification of at least three genetic loci: PGL1. PGL2, and PGL3.3
Although PGLs are usually benign tumors, they occasionally metastasize to the lungs, bones, lymph nodes, and other sites.
