History
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. [23] Waxing and waning of the tumor size may be noted and is attributed to fluctuations in the amount of cystic change within the neoplasm.
Physical Examination
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, [24] on the foot, [25] the base of the tongue, [26] and on the lip. [27] The spinal roots and the cervical, sympathetic, vagus, peroneal, and ulnar nerves are affected most commonly. In a case series from 2013, [28] 50% of patients had involvement of mixed sensory and motor nerves. Superficial neurilemmomas in the skin may display a prominent plexiform (nodular) growth pattern. [29]
A Tinel-like sign was described in 81% of 234 cases of benign solitary schwannomas. [30]
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, [31] 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.
A small, clinically freely movable neurilemoma found in the subcutaneous tissue. Note the pale-yellow, somewhat-translucent cut surface. The tumor also exhibits a slight nodular growth pattern on the cut surface. Courtesy of the Atlas of Tumor Pathology Armed Forces Institute of Pathology Fascicles, Tumors of the Peripheral Nervous System. Used with permission.
A larger neurilemoma (5 cm in diameter) arising from a peripheral nerve showing irregularly lobulated and secondary degenerative changes, ie, partly cystic with calcification (the so-called ancient change). Hemorrhage and opaque creamy-yellow areas of tumor are also seen on this cut surface.
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.
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A schematic illustration of the essential microscopic features of a neurilemoma (schwannoma). A solid lesion arises within a nerve composed of a single fascicle (top). The tumor is composed of Schwann cell proliferation within the epineurium and peripherally displaced nerve fibers, resulting in nodular eccentric growth (middle). No capsule is formed in the early growth phase. The larger tumor (bottom) slightly increases the size of the parent nerve and eventually becomes separated from surrounding fascicles by a capsule formed from the perineurium and epineurium. Occasional axons are present.
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A small, clinically freely movable neurilemoma found in the subcutaneous tissue. Note the pale-yellow, somewhat-translucent cut surface. The tumor also exhibits a slight nodular growth pattern on the cut surface. Courtesy of the Atlas of Tumor Pathology Armed Forces Institute of Pathology Fascicles, Tumors of the Peripheral Nervous System. Used with permission.
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A larger neurilemoma (5 cm in diameter) arising from a peripheral nerve showing irregularly lobulated and secondary degenerative changes, ie, partly cystic with calcification (the so-called ancient change). Hemorrhage and opaque creamy-yellow areas of tumor are also seen on this cut surface.
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Cut surface of an intradermal plexiform (nodular) variety of neurilemoma. The plexiform variants of neurilemoma are rare. The area of nodularity is clearly discernible. Courtesy of the Atlas of Tumor Pathology Armed Forces Institute of Pathology Fascicles, Tumors of the Peripheral Nervous System. Used with permission
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A low-power photomicrograph of a dermal plexiform neurilemoma showing nodular aggregates of tumor cells and surrounding loose, myxomatous fibrous stroma. Hematoxylin and eosin stain at 50X magnification.
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Photomicrograph of a neurilemoma from an area with a typical Antoni type A pattern. The palisaded benign Schwann cells show nuclear crowding, with cell processes radiating toward the centers of aggregated tumor cells. Inconspicuous loose fibrous stroma is present at the periphery. Hematoxylin and eosin stain at 150X magnification.
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A photomicrograph showing a characteristic Verocay body of a neurilemoma, consisting of tight, discrete aggregates of spindle-shaped, palisaded nuclei with a central fibrillary area, representing collections of cytoplasmic processes of tumorous Schwann cells. Courtesy of the Atlas of Tumor Pathology Armed Forces Institute of Pathology Fascicles, Tumors of the Peripheral Nervous System. Used with permission.
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Transmission electron micrograph of Antoni type A tumor tissue consisting of prominent arrays of Schwann cell processes with basement membrane substance coated on their surfaces. Note the centrally located nucleus with vesicular nuclear chromatin. Uranium acetate and lead citrate stain at 15,000X magnification.
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A transmission electron micrograph of a Luse body, ie, typical collagen fibrils and adjacent basement substance. Note the long-spaced, 130-nm periodicity. Uranium acetate and lead citrate stain at 52,500X magnification. Courtesy of the Atlas of Tumor Pathology Armed Forces Institute of Pathology Fascicles, Tumors of the Peripheral Nervous System. Used with permission.
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A photomicrograph of a dermal neurilemoma with anti–S-100 protein immunostaining. The tumorous Schwann cells exhibit uniformly positive staining. Immunoperoxidase stain at 150X magnification.
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Solitary cutaneous plexiform neurilemoma shown on photomicrograph.
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Management algorithm for schwannoma nerve graft.
