Paraganglia are clusters of neuroendocrine cells that comprise the sympathetic ganglia, the parasympathetic ganglia, and the adrenal medulla. A paraganglioma (PGL) is a tumor that derives from paraganglia.
The term pheochromocytoma (PHEO) is applied to catecholamine-secreting paragangliomas of the adrenal gland.
Extra-adrenal paragangliomas (ePGLs) may be categorized as either sympathetic (usually found in the abdomen) or parasympathetic (usually found in the head and neck; hnPGL) paragangliomas.
PHEOs and ePGLs most commonly present with hypertension, headache, anxiety, and/or palpitations.
hnPGLs usually present as an enlarging mass or with a mass effect such as a cranial nerve palsy (eg, Horner syndrome).
PGLs have an estimated prevalence of 1 in 5000 and an estimated incidence of 1 in 30,000.
It is important to distinguish the multiorgan system syndromes that include PHEO or PGLs as a single feature (ie, von Hippel-Lindau [VHL], neurofibromatosis [NF], and multiple endocrine neoplasia [MEN]), from the familial tumor predispositions in which these tumors are the predominant feature (Table 47-1).
Table 47-1Genetic Differential Diagnosis |Favorite Table|Download (.pdf) Table 47-1 Genetic Differential Diagnosis
|Syndrome ||Gene Symbol ||Relative Frequency ||Associated Findings |
|von Hippel-Lindau (see Chap. 129) ||VHL ||20%-40% ||Hemangioblastomas of the brain, spinal cord, and retina; renal cysts and clear cell renal cell carcinoma; and endolymphatic sac tumors. Risk of PHEO and other features are mutation specific. Mean age of PHEO is 29 years (PGL is rare). |
|Neurofibromatosis, type 1 (see Chap. 108) ||NF1 ||5%-15% ||Cutaneous neurofibromas, plexiform neurofibromas, cafe-au-lait macules, axillary and inguinal freckling, Lisch nodules (iris hamartomas), optic glioma, sphenoid dysplasia, tibial pseudarthrosis, first-degree relative with NF1. Pheochromocytomas occur in approximately 1% of NF1 patients. |
|Multiple Endocrine Neoplasia, Type 2 (MEN2A) (see Chap. 81) ||RET ||5%-15% ||Medullary thyroid carcinoma (MTC), parathyroid adenoma/hyperplasia. PGLs typically present around age 40 years (decades after medullary thyroid tends to present), is confined to the adrenal gland, has low metastatic potential, and tends to secrete increased amounts of epinephrine. |
|PGL1 ||SDHD ||20%-30% ||PGLs are predominantly hnPGL (80%) but PHEOs (18%), ePGL (2%), and GIST (rare) also occur. The estimated penetrance of hnPGL is 80% and of PHEO is 30%. Parent of origin effect is observed. |
|PGL2 ||SDHAF2 ||Rare ||Primarily, if not exclusively hnPGLs. Parent ...|
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