Paragangliomas

• Paragangliomas are generally benign, slow growing tumors arising from widely distributed paraganglionic tissue thought to originate from the neural crest.
  
• Paraganglia are distributed throughout the head and neck and superior mediastinum along the course of the major vasculature.
  
• Paraganglia are also found in the orbit, the larynx, and along the course of the vagus nerve.
• All paragangliomas are closely related to one another and to pheochromocytomas of the adrenal gland.
• Approximately 90% of tumors arising from the paraganglion system are in the adrenal gland and these tumors are termed pheochromocytoma.
• Nuclear pleomorphism and cellular hyperchromatism are common in paragangliomas and should not be considered evidence of malignancy. Malignancy can not be determined histologically but is reserved for the presence of local, regional or distant metastasis.

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