Dermatologic Manifestations of Neurilemmoma (Schwannoma) Clinical Presentation
- Author: Kara Melissa T Torres, MD, DPDS; Chief Editor: Dirk M Elston, MD more...
While neurilemmomas almost always occur as solitary lesions with no associated genetic syndrome, in some instances they are multiple or occur in association with neurofibromatosis, particularly neurofibromatosis (NF) type 2. Rare examples are associated with NF1 (ie, von Recklinghausen disease).
Patients generally report an asymptomatic slow-growing tumor that has been present for several years. Pain, tenderness, and paresthesia may be expected if the tumor is large or, by virtue of a deep-seated location, is impinging on neighboring structures. Symptoms have been reported in up to one third of patients. Waxing and waning of the tumor size may be noted and is attributed to fluctuations in the amount of cystic change within the neoplasm.
Neurilemmomas have a predilection for the head, neck, and flexor surfaces of the upper and lower extremities. Case reports describe solitary schwannomas in a subungual (under the nailbed) location, on the foot, and on the lip. The spinal roots and the cervical, sympathetic, vagus, peroneal, and ulnar nerves are affected most commonly. In a case series from 2013, 50% of patients had involvement of mixed sensory and motor nerves. Superficial neurilemmomas in the skin may display a prominent plexiform (nodular) growth pattern.
A Tinel-like sign was described in 81% of 234 cases of benign solitary schwannomas.
Neurilemmomatosis or schwannomatosis, a variant of NF2, is an autosomal dominant disorder with full penetrance. Although very few familial cases of neurilemmomatosis have been reported, most (90%) neurilemmomas in this setting have been multiple, encapsulated, and located in the subcutaneous tissue, while 10% have been plexiform, involving the neck, trunk, and extremities.
When the tumor involves small nerves (see the image below), it is freely movable. When the tumor involves large nerves (see the image below), it is movable but moves along the long axis of the nerve where the attachment restricts mobility.
Most neurilemmomas are asymptomatic, nontender, and not associated with neurologic signs or symptoms.
A special form of inherited neurilemmoma (ie, psammomatous melanotic variant) occurs in the setting of Carney complex, which is an autosomal dominant disorder characterized by the combination of spotty pigmentation (ie, lentigines), cardiac myxomas, and endocrine overactivity. More than 50% of patients with a psammomatous melanotic neurilemmoma (ie, schwannoma) have Carney complex. In contrast to the conventional neurilemmoma, the melanotic variant is not associated with NF2; thus, conventional neurilemmomas are not observed in association with Carney complex. Another difference between the two variants is that approximately 10% of melanotic tumors are malignant, whereas conventional neurilemmomas almost never undergo malignant change.
The NF2 gene has been localized to band 22q12. Alteration or loss of the NF2 gene product (also designated as Merlin), a presumed tumor suppressor gene, is central to the pathogenesis of these tumors. Partial or complete monosomy of the chromosome occurs (ie, loss or mutation of both NF2 alleles and mutation of the NF2 gene protein).
The negative staining of neurilemmoma cells by immunohistochemical stain for NF2 protein suggests that loss of NF2 protein function is a prerequisite for neurilemmoma formation.
More than 150 cases of radiation-induced intracranial and peripheral neurilemmomas have been reported. The mean latency period is approximately 20 years, and most of these are solitary tumors.
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