perineurioma
Perineuriomas are rare tumors composed of neoplastic perineural cells. They are found either in the soft tissues, referred to as soft tissue perineurioma or extraneural perineurioma (where they are unassociated with nerves) or arising from peripheral nerves of the limbs or rarely the cranial nerves, in which case they are known as intraneural perineuriomas .
Epidemiology
The epidemiology of perineuriomas depends on their locations.
Soft tissue perineuriomas occur in adults and are more frequent in females (M: F 2:1).
Intraneural perineuriomas are encountered in young adults and adolescents with no sex predilection .
Clinical presentation
Typically patients with intraneural perineuriomas present with muscle weakness . Soft tissue perineuriomas present as deep masses, or in cases of malignant degeneration, metastatic disease, or direct invasion, although this is uncommon .
Pathology
Grading
Soft tissue perineuriomas vary in grade from WHO grade I (benign) to WHO grade II to III (malignant), whereas intraneural perineuriomas are considered WHO grade I lesions .
Malignant perineuriomas are considered variants of malignant peripheral nerve sheath tumors (MPNST) and are also known as MPNST with perineural differentiation .
Macroscopic appearance
Soft tissue perineuriomas appear as well-circumscribed rounded masses .
Intraneural perineuriomas present as a fusiform expansion of a segment of peripheral nerve, ranging greatly in length, but typically longer than 10 cm .
Microscopic appearance
Perineuriomas are composed of neoplastic perineural cells.
Soft tissue perineuriomas demonstrate a whorled arrangement of neoplastic cells, within a collagen background .
Intraneural perineuriomas demonstrate extension of neoplastic perineural cells around axons, largely contained by the endoneurium .
Radiographic features
MRI
Intraneural perineuriomas appear as fusiform enlargement of a nerve with increased T2 signal and contrast enhancement .
Treatment and prognosis
Soft tissue perineuriomas can usually be cured with resection, although local recurrence and metastasis are described in malignant tumors .
Intraneural perineuriomas can be treated conservatively following histological confirmation with biopsy . Alternatively, the mass can be resected with or without nerve grafting .
Differential diagnosis
The differential diagnosis for intraneural perineuriomas includes :
- other neurogenic tumors
- chronic inflammatory polyneuropathy (CIDP)
- hereditary motor and sensory neuropathy (HMSN)
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