10.17. Tumors of Peripheral Nerves
- General features:
- Mass can be displaced at right angles to the course of the nerve
- Mechanosensitivity expressed as paresthesias when stimulating the tumor
- Inability to distinguish a neurofibroma, Schwannoma or malignant tumor by clinical examination
Benign Neural Sheath Tumors
Schwannoma
- General features:
- The most common benign neural sheath tumor
- Higher incidence in women than men
- May develop with Von Recklinghausen's disease (neurofibroma muscle more common)
- Well encapsulated and cause lateral displacement of adjacent fascicles
- Clinical presentation:
- Positive Tinel's sign (paresthesias elicited by mechanical stimulation) over the tumor in the distribution of the affected nerve
- Rare presentation as a neurologic deficit of the affected nerve
- Most common nerves affected:
- Supra greater than infraclavicular components of the brachial plexus
- Axillary and musculocutaneous nerve
- Tibial nerve greater than sciatic nerve in the thigh
- Median > ulnar > radial nerve; proximal portions of nerve > distal
- Pathology:
- Schwannomas putatively arises from Schwann cells:
- Hypercellular compact or palisading regions (Antoni Type A)
- Verocay bodies are prominent
- Loose hypocellular regions (Antoni Type B)
- Well encapsulated; displace adjacent fascicles laterally; slow enlargement with rare loss of function
Neurofibroma not associated with Von-Recklinghausen's Disease
- General features:
- The nerve can be displaced side to side, but not longitudinally
- More painful than Schwannomas
- Neurologic deficit at presentation > Schwannoma
- Fusiforme > plexiform (noted in non Von Recklinghausen's disease patients)
- Tinel's signs nearly universal
- Females > males
- R > L side of the body
- Arise from the motor more often than sensory portion of the nerve
- Occur as a localized mass; may involve long segment of the nerve
- No cleavage plane; total removal requires nerve section
- Clinical presentation:
- Location:
- Supraclavicular > infraclavicular brachial plexus, 4:1
- Axillary nerve greater than deltoid
- Pelvic plexus > sciatic nerve in the thigh
- Sciatic nerve in the buttock, peroneal and tibial nerve have equal incidence
- Painful particularly if partially resected
- Tinel's sign in the distribution of the nerve
- Pathology:
- Arise from the perineural fibroblast
- Myo-collagenous background that stains intensely with reticulin stain
Neurofibromas Associated with Von Recklinghausen's
- General features:
- Chromosome 17; AD with full penetrance, but variable expression
- Incidence 1/300 persons; often patients have few symptoms
- Females > males; R > L side of the body
- Tumors are found in nerve endings in the skin as well as proximal nerves
- 15% chance of malignant degeneration
- Present at early age than solitary ones
- Clinical presentation:
- Both motor and sensory symptoms
- Anesthesia in the middle of a small neurofibroma of the skin
- Painful; Tinel's usually present
- Location:
- Supraclavicular > infraclavicular brachial plexus, 3:1
- Axillary > musculocutaneous nerve
- Ulnar > median > radial nerve
- Pelvic plexus > sciatic nerve in the thigh
- Tibial > peroneal > saphenous
Plexiform Neurofibroma
- General features:
- Tumors are intrafascicular, extrafascicular with no capsule
- Difficult to operate without further loss of functions
- Most associated with VRD; some are solitary
- Concomitant multiple neurofibromas of the nerve of origin that occur proximally and distally:
- May involve other nerves of the same extremity (neurofibromatosis type 5)
- Malignant transformation in 8% of patients:
- Signaled by pain and rapid growth
- Recurrence following resection is common
Differential Diagnosis Points to Delineate Schwannoma from Neurofibroma
- Neurofibroma is suspected in the face of other stigmata of VRD (rarely Schwannomas can appear in this setting)
- Neurofibroma more local and radicular pain
- Tinel's sign is prominent in both
- Incidence of Schwannoma higher in women than men
- Both displace nerves side to side but not longitudinally
- Neurologic deficit at the time of presentation favors Schwannoma
Neurothekeoma
- General features:
- Benign nerve sheath tumor
- Occurs in patients less than 30 years of age
- Clinical presentation:
- Mistaken for Schwannomas
- Soft mobile tumors of the dermis
- Pathology:
- Schwamm cell or perineural cell origin
- Tumor cells in fascicles circumscribed by a myoid stroma
Benign Non-Neural Sheath Tumors
Dermoids
- General features:
- Arise from muscle
- Abdominal wall as well as neck, shoulder, and extremity location
- May compress or adhere to nerves
- Involve soft tissues
- Do not metastasize
- Clinical presentation:
- Very firm lesions; tight adherence to nerves with consequent deficit
- Pathology:
Myositis Ossificans
- General features:
- Idiopathic form; abnormal calcification starts in the lumborum quadratus (paraspinal muscles)
- Large separation of the great and second toe
- May be related to trauma or previous surgery
- Clinical presentation:
- Neural and vascular tissues may be involved which present with specific local symptoms
- Compresses nerves
- Pathology:
Myoblastoma
- General features:
- Spread as a sheet of tumorous tissue that can envelop or adhere to nerves
- Clinical presentation:
- Pathology:
- Compact angular cells with acidic granules
Lymphangioma
- General features:
- Spread of tumor around nerves
- Clinical presentation:
- Median and ulnar nerve; brachial plexus are major locations of the tumor
- Pathology:
- Sheets of lymphoid type cells
Lipoma
- General features:
- Subcutaneous location
- Sites; forearm (posterior interosseous nerve compression; popliteal fossa (peroneal palsy); supraclavicular fossa, buttock, leg or arm
- Clinical presentation:
- Rarely involves major nerves except when they arise from deep tissue planes
- Median nerve most commonly affected
- Cauda equina involvement is usually asymptomatic unless there is malignant degeneration
- Pathology:
Lipohamartoma
- General features:
- Clinical presentation:
- Involves the median nerve at the wrist or in the palm with median nerve dysfunction
- Pathology:
- Normal fatty tissue
- Tumor may envelop the nerve
Hemangiopericytoma
- General features:
- May originate within the nerve; usually symptoms produced by compression
- Usually arise in the mediastinum
- May metastasize to normal tissue
- Clinical presentation:
- Brachial plexus compression (from mediastinum)
- Upper extremity nerves
Hemangioma
- General features:
- Benign vascular neoplasm; closely resembles normal tissue
- May be found in all organs of the body
- High or low flow characterization by MR angiography
- Clinical presentation:
- May compress adjacent nerves
Ganglions
- General features:
- Arise form joints and may compress contiguous nerves
- Tender mass that causes pain and paresthesias of the affected nerve
- Clinical presentation:
- Compress adjacent nerves at the following levels:
- Thenar sensory branch of the median nerve
- Ulnar palmar branch
- Median and ulnar major trunk's
- Radioulnar (posterior interosseous)
- Knee (peroneal nerve)
- Ankle (posterior tibial nerve)
- Hip (sciatic nerve)
- Shoulder (brachial plexus); suprascapular nerve at the scapular notch
- Elbow; radial > median > ulnar nerve
Ganglions without Joint Connection
- Deep peroneal nerve over the head of the fibula
- Intraneural ganglions:
- Extend great distances with the nerve
- Cause motor and sensory deficits
Epidermoid Cysts
- General features:
- Clinical presentation:
- Sciatic nerve is the commonest location at the:
- Sciatic notch
- Posterior popliteal fossa
Hypertrophic Neuropathy
- General features ("onion-whorl disease"):
- Encasement of the fascicles and individual nerve fibers
- Possible endoneurial proliferation
- Clinical presentation:
- Affects children or young adults
- Peroneal and median nerves are most often affected; rarely the brachial plexus, ulnar radial and sciatic nerves are involved
- Pain and loss of affected nerve's function
- EMG:
- Nerve action potentials can be maintained across the affected part of the nerve
- Pathology:
- Proliferation of perineural cells
- Endoneural fibrosis fibrotic replacement of the perineurium
- Decreased myelin
Malignant Neural Sheath Tumors (MNSTs)
- General features:
- Malignant Schwannoma or neurofibroma (neurogenic sarcoma or fibrosarcoma as alternate designations)
- Mitotic activity, cellular pleomorphism, necrosis and hemorrhage within the tumor
- Heterogeneous cells noted in 15% of MNSTs; neurofibroma > Schwannoma
- 50% of MNSTs arise in VRD; spontaneous solitary lesions occur without VRD
- Malignant degeneration of benign Schwannoma rarely occurs
- Previous radiation is a risk factor
- Clinical presentation:
- Firmer than benign neural sheath tumors
- Mass with irregular borders
- Progressive loss of function of the affected nerve
- Adherent to adjacent structures
- Earliest manifestation is pain
- Rapid increased in size
- May present with metastasis in lung, bone or liver
- Recurrence after treatment with X-ray and chemotherapy is high
Local and Malignant Schwannoma (Neurosarcoma)
- Brachial plexus > sciatic nerve > femoral and ulnar > tibial and peroneal nerve
- Location of malignant neurofibroma (fibrosarcoma)
- Brachial plexus > femoral nerve
- Location of neuroblastoma
Metastatic Carcinoma to Nerves
- General features:
- Direct extension from the primary site
- Breast cancer the most common; also occurs with lung, melanoma, thymoma and pancreatic cancer
- Most metastasis occur in the brachial plexus
- Breast cancer:
- At the infraclavicular axillary level it occurs by direct extension
- At the supraclavicular plexus occurs from lymph nodes
- Pulmonary cancer:
- Pancoast tumor involves the brachial plexus by direct extension (4th/5th finger burning pain, Horner's syndrome, hand weakness; involvement of the lower trunk and sympathetics from C8–T1)
- Hematogenous metastasis to nerve:
- Lymphoma
- Bladder cancer
- Melanoma
Differential Diagnosis of Benign Non-Neural Sheath Tumors
- Ganglioneuroma
- Myoblastoma
- Lipoma
- Meningioma
- Desmoid
- Cystic hygroma
- Epidermoid cyst
- Ganglion cyst
- Hemangioma
- Hemangiopericytoma
- Glomus tumor
- Hemangioblastoma
- Myositis ossificans
- Osteochondroma
- Hidradenitis
- Lymphangioma
- Venous angioma
- Titin tumor
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