Peripheral Nerve Sheath Tumors

Question 1

What do most peripheral nerve tumors develop from?

Answer 1

Schwann cells

Question 2

Schwannomas

Answer 2

Benign encapsulated tumors that may occur in soft tissues, internal organs and/or spinal nerve roots

• most commonly affected cranial nerve root is the vestibular portion of CN8

Question 3

What is the risk for familial neurofibromatosis type 2 patients?

Answer 3

Developing multiple shcwannomas , meningiomas and/or ependymomas

*presence of bilateral vestibular schwannomas is a hallmark sign for neurofibromatosis type 2

Question 4

Pathogenesis of neurofibromatosis type 2

Answer 4

Autosomal dominant loss of function mutation of the NF2(Merlin) gene on chromosome 22
- gene acts to create cytoskeletal proteins that function as tumor suppressors in the nervous system

Question 5

Antoni A and B areas in schwannomas

Answer 5

Antoni A = dense areas of tumor tissue
- possess verocay bodies (alternating bands of nuclear bands : anuclear bands)

Antoni B = loose areas of tumor tissue

schwannomas usually possess both and are comprised of neoplastic Schwann cells

Question 6

3 types of neurofibromas

Answer 6

Localized cutaneous neurofibromas

• usually superficial
• often associated neurofibromatosis type 2

Plexiform neurofibromas

• grow within the confines of a nerve or nerve plexus
• always associated with neurofibromatosis type 1
• small chance, but is the only one that can metastasis
• seen in multiple nerve fascicles

Diffuse neurofibromas

• large masses that are all over the body
• often associated neurofibromatosis type one

Question 7

Pathogenesis of neurofibromatosis type 1

Answer 7

Autosomal dominant disorder that causes mutations in neurofibromin found in the long arm of chromosome 17
- neurofibromin is a negative regulator of the potent oncoprotein Ras (tumor protein that is upregulated in cancer cells to cause unmarked cell proliferation)

Question 8

Symptoms of neurofibromatosis type 1

Answer 8

Learning disabilities

Seizures
Skeletal abnormalities

Vascular abnormalities

Pigmented iris

Pigmented skin lesions

Question 9

Malignant periphery nerve sheath tumors

Answer 9

Only seen in adults

Show evidence of Schwann cell deviation
-usually arise from plexiform neurofibromas

Very heavily tied to neurofibromatosis type 1