L7 Peripheral Neve Tumor

Question 1

The vast majority of Peripheral Nerve Sheath Tumors are composed of cells that show evidence of ?

Answer 1

Schwann cell differentiation.

Question 2

common types of Peripheral Nerve Sheath Tumors are?

Answer 2

1. Schwannoma
2. Neurofibroma
3. Malignant peripheral nerve sheath tumor (MPNST)

Question 3

Peripheral Nerve Sheath Tumors

Answer 3

-occur in adults
-association with the familial tumor syndromes neurofibromatosis type 1 (NF1) and neurofibromatosis type 2 (NF2)

Question 4

Neurofibromatosis Type 1

Answer 4

1-NF1 is an autosomal dominant disorder caused by mutations in the tumor suppressor neurofibromin

2-Disruption of neurofibromin function and resulting Ras hyperactivity which is cardinal feature of NF1-associated tumors.

3-It is a systemic disease associated with non-neoplastic manifestations and with a variety of tumors.

(Neurofibromin is a negative regulator of the potent oncoprotein Ras and encoded on In long arm of chromosome 17 (17q)

Question 5

The tumors associated with Neurofibromatosis Type 1 are?

Answer 5

1. Neurofibromas (all three types)
2. Malignant peripheral nerve sheath tumors
3. Gliomas of the optic nerve
4. Pheochromocytomas

Question 6

Clinical features of NF type 1?

Answer 6

• Mental retardation
• Seizures
• Skeletal defects
• Pigmented nodules of the iris (Lisch nodules)
• Cutaneous hyperpigmented macules (café au lait spots)

Question 7

Neurofibromatosis Type 2?

Answer 7

• autosomal dominant disorder resulting in range of tumors
• dominant loss of function mutation of the merlin gene on chromosome 22.
• Merlin is a cytoskeletal protein that functions as a tumor suppressor by facilitating E- cadherin– mediated contact inhibition.

Question 8

The tumors associated with Neurofibromatosis Type 2 are:

Answer 8

1. Bilateral eighth-nerve schwannomas
2. Multiple meningiomas.
3. Ependymomas of the spinal cord

Question 9

1- benign encapsulated tumor
2- most commonly affected cranial nerve is the vestibular portion of the eighth nerve
3- associated with symptom : hearing loss
4- Most cases are sporadic
5- about 10% are associated with familial NF type 2
Morph:
6-circumscribed masses.
7-admixture of dense and loose areas referred to as Antoni A ( dense ) and B ( loose )

Answer 9

Schwannoma of VIII

Question 10

Neurofibromas subtypes?

Answer 10

1. Localized cutaneous neurofibromas
2. Plexiform neurofibromas
3. Diffuse neurofibromas

(They are benign peripheral nerve sheath tumors) all with NF1

Question 11

superficial nodular or polypoid tumors
occur either as solitary sporadic lesions or as often
multiple lesions in the context of NF type 1?

Answer 11

Localized cutaneous neurofibromas

Question 12

1-Grow diffusely within the confines of a nerve or nerve plexus.
2- Surgical enucleation of such lesions is difficult and associated with lasting neurologic deficits.
3- are virtually pathognomonic for NF1

Answer 12

Plexiform neurofibromas

—-Unlike other benign nerve sheath tumors, these tumors are associated with a small but real risk of
malignant transformation

Question 13

Diffuse neurofibromas?

Answer 13

-infiltrative proliferation
-large, disfiguring subcutaneous masses
-often associated with NF1

1- not encapsulated
2-appear circumscribed as in localized cutaneous neurofibromas, or exhibit a diffuse infiltrative growth pattern.
3-neoplastic Schwann cells in neurofibroma are admixed with other cell types:
mast cells
fibroblast-like cells
perineuriallike cells
4- The cellular growth pattern of neurofibromas ismore haphazard than that of schwannomas

Question 14

Malignant Peripheral Nerve Sheath Tumors:

Answer 14

-arise from transformation of a neurofibroma, usually of the plexiform type.
- one half of such tumors arise in patients with NF1

-large, poorly defined soft tissue masses.

-highly cellular and exhibit anaplasia, necrosis, infiltrative growth pattern, pleomorphism, and high proliferative activity

Question 15

Traumatic neuroma ?

Answer 15

1-is a non-neoplastic proliferation
2-associated with previous injury of a peripheral nerve.
3- Injuries that lead to the transection of axons activate a regenerative program characterized by:
sprouting and elongation of processes from the proximal axonal stump.
4-severe injuries that disrupt the perineurial sheath, these new processes may “miss” their target, distal end of the transected nerve.
5- misguided elongating axonal processes can induce a reactive proliferation of Schwann cells, leading to the formation of a painful localized nodule

(consists of haphazard mixture of axons, schwann cells and connective tissue)