Schwannoma

[Green Grass]

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Yesterday in class, my professor stated that "Schwannomas are the only tumors of peripheral nerves". Why is this? I understand there really isn't much to a nerve (axons, microtubules, fibroblasts, etc.), but why are schwann cells the only ones that can become tumorous?

 

[skelleftea]

Hm, a book on soft tissue sarcoma says that perineurial cells (that support the nerve) and Schwann cells are different and that the Schwann cells express an S-100 protein but not epithelial membrane antigen (vice versa in the perineural cells) - so maybe that S-100 protein is needed for tumor formation?

But then I read this and was confused as the authors seem to suggest that there are other types of peripheral nerve tumors?

http://www.nature.com/modpathol/journal/v16/n4/full/3880761a.html

Sorry to not be able to be more help...

 

[bodonid]

Yesterday in class, my professor stated that "Schwannomas are the only tumors of peripheral nerves". Why is this? I understand there really isn't much to a nerve (axons, microtubules, fibroblasts, etc.), but why are schwann cells the only ones that can become tumorous?

Neruofibromas, while also arising from Schwann cells, are definately a distinct entity.

The reason neurons can't form peripheral nerve tumors is that their cell bodies aren't in the peripheral nerves.

I don't know/understand why you don't get perineurial fibroblast sarcomas.

 

[GeraldMonroe]

Perhaps whatever locks neurons out of the cell cycle and prevents them from replicating makes it incredibly unlikely for a neuron to be capable of unconstrained growth.

"Whatever" includes the presence of regulatory proteins and/or various epigenetic mechanisms.

 

[Green Grass]

Thanks for the responses! I appreciate it.

 

[cpants]

Perhaps whatever locks neurons out of the cell cycle and prevents them from replicating makes it incredibly unlikely for a neuron to be capable of unconstrained growth.

"Whatever" includes the presence of regulatory proteins and/or various epigenetic mechanisms.

Neurons can form malignant tumors. It just happens in the CNS. There are no neuronal cell bodies in the peripheral nerves. The Schwann cells are basically the only cells around to form tumors in the peripheral nerves.

 

[coffeebythelake]

The reason neurons can't form peripheral nerve tumors is that their cell bodies aren't in the peripheral nerves.

Dorsal root ganglia are most definitely PNS.

 

[Dirt]

Perhaps whatever locks neurons out of the cell cycle and prevents them from replicating makes it incredibly unlikely for a neuron to be capable of unconstrained growth.

"Whatever" includes the presence of regulatory proteins and/or various epigenetic mechanisms.

Bingo. You don't see terminally differentiated red cells forming tumors either do you?

 

[GeraldMonroe]

Bingo. You don't see terminally differentiated red cells forming tumors either do you?

Also, there's a lot more neurons (orders and orders of magnitude) in the brain versus the PNS, and some of the neurons are capable of cell division. Thus, occasionally they can form tumors, although I think the majority of brain tumors come from glial cells.

 

[Dirt]

although I think the majority of brain tumors come from glial cells.

The vast, vast majority.

 

[bodonid]

Dorsal root ganglia are most definitely PNS.

yeah, yeah, I thought somebody was going to say that. But they don't form tumors, so I decided not to add that.

 

[bubbachuck]

in case someone was wondering the difference b/w Schwannoma vs. Neurofibroma. Both arise from Schwann cells but according to Wikipedia, neurofibromas "incorporate many additional types of cells and structural elements in addition to Schwann cells, making it difficult to identify and understand all the mechanisms through which they originate and develop." (Source: http://www.ihcworld.com/_newsletter/2004/2004-10_NF_vs_schwannoma_v1.pdf)

SO...basically no one knows WHY they're different but they look different.

A doctor online tries to explain to a lady what the difference is...he says "they just arise from different cells in the peripheral nerve," which appears to not be correct.

Boards review:
Neurofibroma - think Neurofibromatosis 1, tumor contains lots of stuff
Schwannoma - think Neurofibromatosis 2, VIII compression, tumor purely consists of Schwann cells

Hmm...finally I know why it's called Neurofibromatosis.

 

[TMP-SMX]

Neurofibroma is within the nerve itself. A schwannoma is outside/within the nerve sheath. An acoustic neuroma is a misnomer as it isn't actually part of the nerve.

 

[Blesbok]

Neurofibroma is within the nerve itself. A schwannoma is outside/within the nerve sheath. An acoustic neuroma is a misnomer as it isn't actually part of the nerve.

A neurofibroma arises from the schwann cells, not the nerve.

 

[bubbachuck]

An acoustic neuroma is a misnomer as it isn't actually part of the nerve.

yea good catch, I'll cite wikipedia again: "The correct medical term is vestibular schwannoma, because it involves the vestibular portion of the 8th cranial nerve and it arises from Schwann cells, which are responsible for the myelin sheath in the peripheral nervous system."

Neurofibromatosis 2! Bilateral!

 

[TMP-SMX]

A neurofibroma arises from the schwann cells, not the nerve.

Right, but the growth pattern makes a schwannoma much easier to remove than a neurofibroma. Neurofibromas interweave themselves within the nerve itself and therefore it is hard to remove it without sacrificing the nerve. This is the point I'm making.