DEFINITION AND PATHOGENESIS
- Solitary lesion (90%) or occurring in von Recklinghausen's disease (10%) of Schwann cells
- Storiform perineural fibroma
- Pacinian neurofibroma
- Epithelioid neurofibroma
- Pigmented neurofibroma ---melanocytic differentiation (both Schwann cells and melanocyte of neural crest origin)
- Large lesions (>4cm) may not be benign and require resection after workup
- Commonly associated with neurofibromatosis
- ~5% of benign soft tissue tumors
- M=F to slight M preponderance reported
- Most patients 20-30 years of age
- Most superficial dermal or subcutaneous lesions
- Solitary spinal neurofibroma may present with radicular sxs
- Has been reported occurring in the same nerve trunk as a neurilemoma
- MRI best demonstrates ovoid lesion that is well circumscribed
- Spinal lesion x-ray may show pedicle or vertebral body erosion, ? interpedicular distance, laminae(e) distortion, neural foramenal enlargement
- Myelography: "amputation" of nerve root with a filling defect
- US: well-defined hypoechoic lesion
- CT: intra- and extraspinal "hour-glass" appearance
- Hypodense to muscle
- Enhances with contrast
- T1-weighted images show intensity of lesion slightly higher than muscle
- T2-weighted images show signal (peripheral > central) with bright non-uniform gadolinium DPTA enhancement (peripheral > central)("target sign")
- Grayish-white to yellow-brown
- Not encapsulated (unlike neurilemmoma)
- May be myxomatous to hard and rubbery
- Lack two distinct zones (unlike neurilemmoma)
- Interlacing elongated cell bundles with wavy nuclei of varying cellularity
- Arrangement of cells in fascicles, whorls, or storiform
- Schwann cells with a large nuclei, little cytoplasm, and pronounced basal lamina
- Fibroblast-like cells and mast cells also are present
DIFFERENTIAL CLINICOPATHOLOGIC DIAGNOSIS
- Neurilemoma (S-100 usually negative, unlike neurilemoma)
DISEASE COURSE AND TREATMENT
- Simple excision
- Residual numbness should be warned about, esp in digital locations (where grafting may be appropriate)
- Risk of malignant degeneration small, esp in solitary lesions
- (Nerve sheath myxoma)
- Involve head, neck, and shoulder, arising in childhood
- Usually superficial
- Lobular areas of myxoid material with neural cell differentiation demonstrated by EM
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