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Old 05-09-2011
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Question Episodic hypertension in pheochromocytoma

Why does pheochromocytoma present with episodic hypertension and neuroblastoma does not? Seems like they both would since they secrete catecholamines?
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Old 05-09-2011
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That's a very interesting question. I have no idea about the answer. I even tried searching for it, but couldn't find the answer. I will let you know if I can find one. However it may be due to the fact that neuroblastoma is usually malignant while pheococytoma is usually benign. Malignant tumors tend to be less differentiated and thus are likely to produce lesser quantities of hormones. But I have no idea whether I'm even on the right track here.
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Old 05-09-2011
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Catecholamine secretion in pheochromocytomas is not regulated in the same manner as in healthy adrenal tissue. Unlike the healthy adrenal medulla, pheochromocytomas are not innervated, and catecholamine release is not precipitated by neural stimulation. The trigger for catecholamine release is unclear, but multiple mechanisms have been postulated, including direct pressure, medications, and changes in tumor blood flow.

In Neuroblastoma, the story is different. It's not an adrenal gland tumor, it's a neural crest tumor that can be found anywhere and that can secrete a variety of hormonal and non-hormonal compounds. When it secretes catecholamines it usually does so in a continuous fashion.
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Old 05-09-2011
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Quote:
Originally Posted by Hokolesqua View Post
Catecholamine secretion in pheochromocytomas is not regulated in the same manner as in healthy adrenal tissue. Unlike the healthy adrenal medulla, pheochromocytomas are not innervated, and catecholamine release is not precipitated by neural stimulation. The trigger for catecholamine release is unclear, but multiple mechanisms have been postulated, including direct pressure, medications, and changes in tumor blood flow.

In Neuroblastoma, the story is different. It's not an adrenal gland tumor, it's a neural crest tumor that can be found anywhere and that can secrete a variety of hormonal and non-hormonal compounds. When it secretes catecholamines it usually does so in a continuous fashion.
Could you elaborate a bit more? I am not able to perceive the idea you are trying to make..
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Old 05-09-2011
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Actually, both pheochromocytoma and neuroblastoma's are derived from neural crest cells. However, pheo's are strictly neoplasms of chromaffin cells while neuroblastoma's can originate from either the adrenal medulla or along the sympathetic chain, hence they are neuroblastic tumors. According to Robbin's pathology:
"About 90% of neuroblastomas, regardless of location, produce catecholamines (similar to the catecholamines associated with pheochromocytomas), which are an important diagnostic feature (i.e., elevated blood levels of catecholamines and elevated urine levels of the metabolites vanillylmandelic acid [VMA] and homovanillic acid [HVA]). Despite the elaboration of catecholamines, hypertension is much less frequent with these neoplasms than with pheochromocytomas".
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