Everything about Paraganglioma totally explained
A
paraganglioma is a rare
neoplasm that can be found in the abdomen, thorax, and in the head and neck region. They are usually considered
benign and complete surgical removal results in cure. However, in about 3% of cases they're
malignant and have the ability to
metastasize. Paragangliomas are still sometimes called
glomus tumors (not to be confused with
glomus tumors of the skin) and
chemodectomas, but paraganglioma is the currently accepted and preferred term.
Presentation
Paragangliomas arise from the
glomus cells, which are special
chemoreceptors located along blood vessels that have a role in regulating blood pressure and blood flow. The main concentration of glomus cells are found are in the
carotid body, located in the upper neck at the branching of the
common carotid artery, and the
aortic bodies, located near the
aortic arch. The glomus cells are a part of the
paraganglion system composed of the extra-adrenal
paraganglia of the
autonomic nervous system, derived from the embryonic
neural crest. Thus, paragangliomas are a type of
neuroendocrine tumor, and are closely related to
pheochromocytomas. Although all paragangliomas contain neurosecretory granules, only about 1-3% have clinical evidence of oversecretion.
Paragangliomas are found predominantly in the abdomen (85%) and the thorax (12%), and only 3% are found in the head and neck region. Most occur as single tumors. When they occur in multiple sites they're usually found as a part of a heritable syndrome such as
multiple endocrine neoplasia types II-A and II-B and
SDH-related mutations.
Classification
According to the
World Health Organization classification of
neuroendocrine tumors, paragangliomas are classified as having a neural cell line of origin. In the categorization proposed by Wick, the paragangliomas belong to Group II.
Inheritance
Familial paragangliomas account for approx. 25% of cases, are often multiple and bilateral, and occur at an earlier age. Mutations of the genes
SDHD (previously known as PGL1),
PGL2, and
SDHC (previously PGL3) have been identified as causing familial head and neck paragangliomas. Mutations of
SDHB play an important role in familial adrenal pheochromocytoma and extra-adrenal paraganglioma (of abdomen and thorax), although there's considerable overlap in the types of tumors associated with SDHB and SDHD gene mutations.
Pathology
The paragangliomas appear grossly as sharply circumscribed polypoid masses and they've a firm to rubbery consistency. They are highly
vascular tumors and may have a deep red color.
On microscopic inspection, the tumor cells are readily recognized. Individual tumor cells are polygonal to oval and are arranged in distinctive cell balls, called
Zellballen. These cell balls are separated by fibrovascular stroma and surrounded by sustentacular cells.
By light microscopy, the differential diagnosis includes related neuroendocrine tumors, such as
carcinoid tumor,
neuroendocrine carcinoma, and
medullary carcinoma of the thyroid; middle ear
adenoma; and meningioma.
With
immunohistochemistry, the chief cells located in the cell balls are positive for
chromogranin,
synaptophysin,
neuron specific enolase,
serotonin and
neurofilament; they're
S-100 protein negative. The sustentacular cells are S-100 positive and focally positive for
glial fibrillary acid protein. By
histochemistry, the paraganglioma cells are argyrophilic,
periodic acid Schiff negative,
mucicarmine negative, and
argentaffin negative.
Clinical characteristics
Paragangliomas are described by their site of origin and are often given special names:
- Carotid paraganglioma (carotid body tumor): Is the most common of the head and neck paragangliomas. It usually presents as a painless neck mass, but larger tumors may cause cranial nerve palsies, usually of the vagus nerve and hypoglossal nerve.
Glomus tympanicum and Glomus jugulare: Both commonly present as a middle ear mass resulting in tinnitus (in 80%) and hearing loss (in 60%). The cranial nerves of the jugular foramen may be compressed, resulting swallowing difficulty. These patients present with a reddish bulge behind an intact ear drum. This condition is also known as the "Red drum". On application of pressure to the external ear canal with the help of a pneumatic ear speculum the mass could be seen to blanch. This sign is known as "Brown's sign".
Vagal paragangliomas: These are the least common of the head and neck paragangliomas. They usually present as a painless neck mass, but may result in dysphagia and hoarseness.
Other sites: Rare sites of involvement are the larynx, nasal cavity, paranasal sinuses, thyroid gland, and the thoracic inlet, as well as the bladder in extremely rare cases.
Treatment
The main treatment modalities are surgery, embolization and radiotherapy.
Further Information
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