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Paraganglia are highly vascular structures derived from the neuroectoderm and have chromaffin cell origin. Grossly, most are microscopic. The largest are usually in the organ of Zuckerkandl or carotid body and are normally a few millimeters in size.
Paraganglia are located in intimate proximity with the two limbs of the autonomic nervous system:
- Parasympathetic system (chemoreceptor function)
-Head and Neck
- Sympathetic system (similar function to adrenal medulla)
-Retroperitoneum along the thoracolumbar paravertebral region
-Within viscera - urinary bladder and gallbladder
Normal location of paraganglia (borrowed from Lee et al, "Extraadrenal Paragangliomas of the Body: Imaging Features" AJR 2006)
Vascular tumors that arise from the paraganglia are now called paragangliomas. The term, "paraganglioma," has superceded the names of paraganglia of various sites throughout the body:
- Extraadrenal pheochromocytoma
- Glomus Tumor
- Sympathetic nevus
The majority (85%) that arise from the adrenal medulla are known as pheochromocytomas. When they arise from extraadrenal neuroendocrine tissues, the term paraganglioma is used (aka extraadrenal pheochromocytoma).
Usually paragangliomas of the head and neck are not hormonally active (non-functional) and presentation is often with symptoms of delayed compression of nearby structures such as pain and shortness of breath.
In the thorax and abdomen they are more commonly functional. Clinical presentation is with catecholamine hypersecretion, causing:
- Life threatening cardiovascular complications include:
- Myocardial infarction
- Cerebral hemorrhage
- Malignant hypertension
Pheochromocytomas present between the 5th to 7th decade of life with a slight female predilection.
Extra-adrenal paragangliomas present between the 2nd and 3rd decade of life with a slight male predilection.
- Autosomal-dominant with incomplete penetrance
- 30-50% multicentric
- Multiple endocrine neoplasia (MEN IIA and IIB) - 50%
- Neuroectodermal syndromes
- Tuberous sclerosis
- Neurofibromatosis - <5% (TYPE 1)
- Von Hippel-Lindau - 20%
- Carney's triad
- Gastric leiomyosarcoma
- Pulmonary chondroma
- Extraadrenal paraganglioma
- Mutations in the mitochondrial complex II genes SDHB, SDHC, and SDHD
- Up to 40% mortality with vascular invasion
Histologically there are no definite cellular characteristics that differentiate benign from malignant paragangliomas.
Metastasis is the only true marker of malignancy.
The metastatic incidence is reported between 2% to 36% with most common spread to:
- Local lymph nodes
Ten Percent Rule
- 10% extra-adrenal (aka Paraganglioma)
- 10% bilateral (multicentric)
- 10% extra-abdominal
- 10% extra-abdominal
- 10% familial
- 10% pediatric
- 10% not a/w HTN (Clinically Silent)
- Risk of sustained hypertension is higher than in adults
- Extra-adrenal pheochromocytomas are more common in children than in adults
- In children the differential diagnosis includes:
- Neuroblastoma and Ganglioneuromas
- Hypertension is less common with neuroblastomas because the tumors produce a large amount of inactive catecholamine precursors.
1. Balcombe et al, "Cross-Sectional Imaging of Paragangliomas of the Aortic Body and Other Thoracic Branchiomeric Paraganglia" AJR 2007
2. Lee et al, "Extraadrenal Paragangliomas of the Body: Imaging Features" AJR 2006
3. Saurborn et al, "Best Cases from the AFIP: Paraganglioma of the Organs of Zuckerkandl" Radiographics 2003
4. Rao et al, "From the Archives of the AFIP: Paragangliomas of the Head and Neck: Radiologic-Pathologic Correlation" Radiographics1999
5. Van Gils et al, "MR Imaging and MIBG Scintigraphy of Pheochromocytomas and Extraadrenal Functioning Paragangliomas" Radiographics 1991