A neurilemmoma is a benign, usually encapsulated neoplasm derived from Schwann cells and, along with neurofibroma, constitutes one of the 2 most common benign peripheral nerve sheath tumors. The peripheral nervous system can be defined as nervous tissue outside the brain and spinal cord. It extends from the glial-schwannian junction in the cranial nerves and spinal roots to the termination of the nerve fibers in their end organ receptors and includes the posterior root ganglia and those of the autonomic nervous system. Neurilemmomas may affect any location in the course of the peripheral nervous system (ie, cranial and spinal nerve roots, cranial and peripheral nerves, end organ receptors, small nerve twigs). They are common in paravertebral locations and the flexor regions of the extremities (especially near the elbow, wrist, and knee) and occasionally involve the skin. The presence of a noninvasive tumor next to a peripheral nerve suggests the diagnosis of neurilemmoma.
The major forms of neurilemmoma recognized are conventional (common, solitary), cellular, plexiform, ancient forms, and melanotic schwannoma.[1, 2, 3] Specific variants such as plexiform and giant sacral neurilemmoma have been associated with an increased risk of local recurrence following incomplete excision.
Recently, a unique form of plexiform schwannoma consisting of a proliferation of epithelioid and spindled cells positive for S-100, Melan-A, and HMB-45 but no obvious melanin pigmentation, called plexiform melanocytic schwannoma, has also been described.[4] Other rare variants include malignant epithelioid schwannoma without neurofibromatosis,[5] a very rare variant called cutaneous pseudoglandular schwannoma containing glandlike structures formed by neoplastic Schwann cells and containing mucinous material,[6, 7] neuroblastomalike/rosetoid schwannoma,[8] and a variant with a plexiform multinodular pattern.[9]
Other variants are associated with genetic syndromes such as Carney complex (ie, psammomatous melanotic schwannoma); neurofibromatosis (NF) type 2 (NF2, ie, cranial or spinal root neurilemmoma; multiple cutaneous plexiform schwannoma[10] ; neurilemmomatosis (schwannomatosis), which is a variant of NF2 characterized by multiple neurilemmomas and lack of involvement of the vestibular division of cranial nerve VIII; and segmental schwannomatosis, a distinct form of neurofibromatosis characterized by multiple schwannomas localized to one limb.[11] There have also been reports of nerve sheath tumors exhibiting histologic hybrid features of schwannoma and soft-tissue perineurioma.[12]
Of note, the benign nerve sheath tumors are classified as World Health Organization grade I on the basis of their benign cytologic features, in contrast to the malignant counterparts, which are World Health Organization grade III or IV.
The synonym schwannoma is often used interchangeably with neurilemmoma. Other synonyms include neurolemmoma and peripheral fibroblastoma.
An understanding of the relationship of the Schwann cell to other neuronal elements in the peripheral nervous system is helpful in conceptualizing the pathophysiology of a neurilemmoma.
The peripheral nervous system differs from the central nervous system in the nature of its supporting cell; the Schwann cell supports the former and the neuroglial cells support the latter. It is generally accepted that in embryogenesis, the Schwann cells are derived from the neural crest and are of neuroectodermal origin. As the peripheral nerves form, the Schwann cells migrate peripherally from the spinal ganglia, parallel to the axons, and encase them with their cytoplasm. In myelinated fibers, only one axon segment is encased by one Schwann cell.
The myelin sheath is created by a synthesis and wrapping of Schwann cell plasma membrane around the axon. Schwann cells sheath the axons from the point at which the latter penetrate the pia mater to their terminations. Upon penetrating the pia, the neuroglia is lost; the individual nerve fibers pass through a sievelike structure composed of reticulin (young collagen fibers), and, thereafter, each is contained within its ensheathing tube of reticulin and Schwann cell elements.
At this site, perineurial cells (perineural epithelium) also make their appearance. In nonmyelinated nerves, several axon segments are ensheathed by a common Schwann cell. In a fully developed nerve, a layer of connective tissue, or epineurium, surrounds the entire nerve trunk. Several nerve fascicles lie within the confines of the epineurium, and each is surrounded by a well-defined perineurium. The smallest connective tissue unit of the nerve is the endoneurium, which is a network of fibroblasts, blood vessels, and collagen encircling individual nerve fibers).
Neurilemmomas arise within a nerve consisting of a single fascicle. The tumors are composed entirely of the supporting Schwann cells and peripherally displaced nerve fibers, resulting in a globoid eccentric tumor mass. In the early intrafascicular growth phase, small neurilemmomas displace nerve fibers without forming a capsule. The larger tumors increase the size of the parent nerve and become separated from surrounding fascicles by a capsule derived from perineurium and epineurium, as demonstrated in the image.
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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 singl....
Most neurilemmomas are of the conventional (common) type, arise as solitary tumors smaller than 10 cm, and are not associated with a genetic syndrome. They display the classic gross and microscopic features described in Histologic Findings. The cellular variant is rare in the skin, developing more commonly as a tumor of the mediastinum, retroperitoneum, and deep soft tissue. It is composed of a hypercellular mass of spindle-shaped cells forming intertwining fascicles and cords. Mild-to-moderate cytologic atypia and a low mitotic rate (5 mitoses per 20 high-powered fields) are characteristic.
The plexiform variant demonstrates a multinodular growth pattern of predominantly Antoni type A tissue (see Histologic Findings) in the dermis and subcutis. In contrast to plexiform neurofibroma, plexiform neurilemmoma is not pathognomonic of neurofibromatosis and malignant transformation is exceedingly rare. Ancient neurilemmomas are characterized by degenerative changes and cytologic atypia typical of Antoni type B tissue, of which they are almost entirely composed. Despite sometimes striking cytologic atypia, mitotic figures are rare.
Neurilemmomas may occur spontaneously or occur as part of a familial syndrome.[13] Most tumors have shown genetic aberrations (ie, ring chromosome 22).[14]
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.[13, 15] 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.[16] The mean latency period is approximately 20 years, and most of these are solitary tumors.
The exact prevalence of neurilemmomas (benign schwannomas) of all anatomic sites is unknown. It is estimated that about 70% of NF2 patients have skin tumors, the majority of which are schwannomas.[17] Meanwhile, the plexiform variant of this Schwann cell tumor was found to have a 5% association with NF2 and schwannomatosis.[18] Numerous subsequent reports have confirmed that this association is more than coincidental.
Race
No racial predilection is noted for this neoplasm.
Sex
The tumor affects the sexes in roughly equal numbers.[19]
Age
Neurilemmomas occur in persons of any age but are most common in patients aged 20-50 years. The cellular form of neurilemmoma has a peak incidence in the fourth decade of life, and approximately 5% of neurilemmomas occur in childhood and adolescence. Three congenital cases have been reported. In the nearly 50 reported cases of plexiform neurilemmoma, the age ranged from 50 days to 80 years, with a mean of 34 years. In melanotic neurilemmoma, the age range was reported at 10-84 years, with a mean age of 37 years. Overall, approximately 75% of neurilemmomas occur in the first 4 decades of life.
Neurilemmomas behave in a benign fashion. Incompletely excised examples are capable of slow recurrence. Higher recurrent rates are noted with the plexiform and cellular varieties.[20] Locally aggressive behavior is observed in tumors with increased cellularity, higher mitotic rates (mean, 4 per 10 high-power fields), and underlying bone extension (observed in occasional cases of orbital neurilemmoma).
Melanocytic schwannomas of the cervical, thoracic, and lumbar spine reported by Peltier et al[21] demonstrated a guarded prognosis. Two of the 3 cases studied showed unfavorable outcomes, with local recurrence and leptomeningeal metastasis, especially in young patients.
Large tumors (eg, giant sacral schwannomas), contrary to previous literature, have been found to have a low rate of local recurrence and rare malignant transformation.[22] A clinicopathologic study has found that patients with asymptomatic neurilemmomas occurring in association with NF2 not only have more severe neurologic deficits but also have little postoperative improvement and a higher rate of tumor recurrence. Malignant schwannomas (neurofibrosarcoma) arise de novo or in neurofibromas in the setting of neurofibromatosis. They are not regarded to be malignant counterparts of neurilemmomas. Malignant change in neurilemmomas is exceedingly rare.
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.
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.
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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 als....
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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 c....
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.
Microscopic examination of the tumor biopsy tissue and clinicopathologic correlation establishes the correct diagnosis. The diagnostic microscopic features are described in Histologic Findings.
Masson trichrome stain can be used to demonstrate the presence of longitudinal striations observed in smooth muscle tumors to differentiate a cutaneous leiomyoma from a neurilemmoma, which lacks striations.
Immunostaining using anti–S-100 protein antibody confirms the presence of Schwann cells. In addition, vimentin, myelin basic protein, glial fibrillary acid protein (GFAP), and neuron-specific enolase (NSE) are expressed in most cases.[23, 27] On rare occasions, benign schwannomas may express alpha-smooth muscle actin.[32]
With routine radiographic examination, neurilemmomas generally appear as sharply circumscribed tumor masses.
CT scan images show circumscribed, low-attenuation masses with uniform or heterogeneous contrast enhancement.
MRI reveals a high T2 signal and heterogeneous contrast enhancement.
Both CT scan images and MRI show that large tumors often have areas of cystic changes. Benign neurilemmomas do not show active irregular invasion of bone, as is observed in malignant peripheral nerve sheath tumors.
The correct diagnosis of neurilemmoma is established by microscopic examination of tumor biopsy tissue.
Gross appearance
Cutaneous neurilemmomas present usually as a solitary dermal or subcutaneous nodule. However, lesions may be protruding or pedunculated.[33] In general, these lesions are firm, smooth-surfaced, and smaller than 10 cm. Most neurilemmomas affect small nerves. The smaller examples are rounded, somewhat elastic in consistency, and milky-white or semitranslucent. The larger tumors are lobulated irregularly and, by virtue of secondary degenerative changes, become partly or mainly cystic with calcification (ie, ancient change). Areas of hemorrhage and opaque creamy-yellow tumorous tissue are observed on the cut surface (see the image below)
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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 c....
Some tumors manifest as a firm rubbery nodule with a whorled appearance on the cut surface, resembling smooth muscle tumors of the uterus. The plexiform or multinodular variant, which accounts for approximately 5% of neurilemmomas, may be discernible upon gross examination (see the images below).
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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 cl....
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A low-power photomicrograph of a dermal plexiform neurilemoma showing nodular aggregates of tumor cells and surrounding loose, myxomatous fibrous stro....
Microscopic appearance
Most tumors are unilocular masses surrounded by a fibrous capsule composed of epineurium and residual nerve fibers. While this capsule is evident in most tumors, those arising in mucosa (eg, nose, nasopharynx), the central nervous system, and viscera often lack a capsule. Intradermal neurilemmomas and the plexiform or multinodular growth pattern similar to a plexiform neurofibroma are rare. Histologically, the characteristic feature of a neurilemmoma is the pattern of alternating Antoni type A and B areas.
Antoni type A areas (as shown in the image) consist of compact, spindle-shaped cells with twisted nuclei, indistinct cytoplasmic borders, and, occasionally, clear intranuclear vacuoles.
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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 cel....
The cells are arranged in short bundles or interlacing fascicles with nuclear palisading, whirling of the cells, and Verocay bodies. Verocay bodies are formed by 2 compact rows of well-aligned nuclei and cell processes that are arranged in a roughly oval shape (see the image below). Verocay bodies are more distinctive of schwannomas than the Antoni A and Antoni B patterns, but they are not seen in all schwannomas.
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A photomicrograph showing a characteristic Verocay body of a neurilemoma, consisting of tight, discrete aggregates of spindle-shaped, palisaded nuclei....
Mitotic figures are rare. S-100 protein, an acidic protein commonly found in the supporting cells of the central and peripheral nervous system, is demonstrated in neurilemmomas, particularly in the Antoni type A areas. Antoni B areas are less cellular and are often disorderly. The capsule is typically positive for epithelial membrane antigen (EMA).[33] The spindle or oval cells are arranged haphazardly in the loose matrix with microcystic changes, inflammatory cells, and delicate collagen fibers. Prominent, irregularly spaced blood vessels are present in the stroma. The psammomatous melanotic neurilemmoma (schwannoma) shows, in addition to the above features, melanin deposition and concentric calcified bodies (psammoma bodies).
Schwannomas have been variably observed to be GFAP and occasionally keratin positive, with antibodies reacting with multiple keratins (pankeratins, keratin cocktail (CK) (AE1/AE3). Both markers highlighted the cellular Antoni A areas, particularly adjacent to the capsule, myxoid or degenerative areas, and perivascularly. In recent studies of a large series of retroperitoneal schwannomas, 84% of the tumors stained positive for both AE1/AE3 and GFAP. However, the tumor cells were negative for specific keratin polypeptides (K). The findings can be attributed to cross reactivity of AE1/AE3 with other intermediate filament proteins, such as GFAP.[34] Schwannomas contain Leu7 and S-100 protein.
Ultrastructural examination of the tumor reveals almost exclusively a single cell type (ie, Schwann cells). They have characteristic thin cell processes that arrange in undulating layers and are continuous from the cell body. The Schwann cell surface is coated with basal lamina composed of electron-dense material measuring approximately 50 nm (see the image).
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Transmission electron micrograph of Antoni type A tumor tissue consisting of prominent arrays of Schwann cell processes with basement membrane substan....
The basal lamina lies in stacks between the cells along with typical and long-spacing collagen fibrils with a 130-nm periodicity. These collagen fibrils are often referred to as a Luse body (see the image).
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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 periodic....
The cytoplasm contains a flattened and sometimes invaginated nucleus, microfibrils, rare lysosomes, and scattered mitochondria. In Antoni B areas, the Schwann cells have increased numbers of lysosomes and myelin figures and fragmented basal lamina.
Immunohistochemical staining using anti–S-100 protein antibody demonstrates uniformly and intensely positive staining of Schwann cells in the tumor (see the image).
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A photomicrograph of a dermal neurilemoma with anti–S-100 protein immunostaining. The tumorous Schwann cells exhibit uniformly positive staining. Immu....
This technique serves as an important diagnostic tool, and, in severely degenerated neurilemmomas, S-100 protein stain is most valuable for confirming the diagnosis.
The results of immunostaining for myelin proteins used to identify benign and malignant Schwann cell tumors have been variable.
Histologic differential diagnosis
Neurofibroma
The loose, myxomatous Antoni type B tissue of a neurilemmoma may mimic a neurofibroma. However, neurofibromas lack the thick collagenous capsule of neurilemmomas and instead are surrounded by a variably thickened perineurium and epineurium. Neurofibromas also lack the Antoni type A and B patterns and Verocay bodies typical of neurilemmomas. Neurofibromas are composed of a mucinous matrix containing scattered, myelinated, and nonmyelinated axons along with a heterogeneous cell population including Schwann cells, fibroblasts, and perineural cells. Consequently, immunoreactivity for S-100 protein is observed in only a portion of the cells comprising a neurofibroma, as opposed to uniform reactivity throughout a neurilemmoma.
Palisaded encapsulated neuroma
This is an uncommon, generally solitary, asymptomatic intraneural neuroma that may arise in early childhood or adulthood. It appears as a firm, rubbery, skin-colored or pink papule commonly affecting the "butterfly area" of the face. Palisaded encapsulated neuromas are bulbous expansions of a peripheral nerve. They appear as well-circumscribed, ovoid, or rounded nodules in the dermis, which, in contrast to neurilemmomas, contain a greater number of axons and Schwann cells in interlacing fascicles along with characteristic cleftlike spaces.
Schwannoma
These are distinguished from astrocytoma and ependymoma by their abundant parenchymal reticulin, which is positive for type IV collagen. Schwannomas have characteristic contiguous basement membranes along the exterior surfaces of their cells. Although occasionally focal positive staining for GFAP may be present, negative GFAP staining supports the diagnosis of schwannoma. Astrocytomas are generally GFAP positive.
Fibrous meningiomas
These lack typical meningeal whorls and psammoma bodies, and they can be difficult to differentiate from schwannomas. EMA is a useful immunomarker for distinguishing the 2 tumors. Meningiomas are reactive with EMA, while schwannomas (except for their surrounding capsules) are not. GFAP can sometimes be used, because some schwannomas are positive but meningiomas are negative.
Cutaneous leiomyoma
Leiomyomas are benign smooth muscle tumors. They are not derived from neural tissue and generally lack the thick, hyalinized capsule and vasculature of a neurilemmoma. Palisading resembling Verocay bodies may be observed. The blunt-ended nuclei and densely eosinophilic cytoplasm of smooth muscle cells showing distinct cell borders and perinuclear halos help distinguish them from Schwann cells (with their more tapered, spindle-shaped nuclei).
Immunohistochemical stains readily distinguish leiomyomas from neurilemmomas, the former staining with myogenic cell markers, such as smooth muscle actin and desmin, and the latter showing positive staining with S-100. It should be noted that schwannomas have been reported to express actin.[32] Masson trichrome stain may be used to demonstrate the longitudinal striations characteristic of smooth muscle tumors. The ultrastructural features of smooth muscle cells are also highly characteristic, being bounded by a basement membrane and often containing parallel arrays of abundant cytoplasmic microfilaments (actin) with interspersed fusiform dense bodies and pinocytotic vesicles.
Palisaded myofibroblastoma
These contain palisaded cells and Verocay bodies that may mimic neurilemmomas. However, palisaded myofibroblastomas involve lymph nodes, contain fibroblastic and myofibroblastic elements, and are negative for S-100 protein staining.
Given the benign nature of neurilemmomas, therapy is conservative and directed toward sparing the parent nerve when one is identified. The treatment of choice is gross total resection of the tumor. Care should be taken during the surgery, as 75% of patients in a case series were found to have nerve fascicular involvement.[28, 35] In one study, 75% of patients experienced some immediate neurological deficit after excision, due to transection of fascicles that ran through the tumor.[36] An algorithm has been recommended, with nerve grafting as an option for excision of mixed-nerve schwannomas in young patients.[28] See the figure below.
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Management algorithm for schwannoma nerve graft.
Although neurilemmomas are benign, incomplete excision may result in slow local recurrence. Patients with asymptomatic neurilemmomas occurring in association with NF2 frequently present with more severe neurologic deficits. These patients have a high rate of recurrence and less postoperative improvement. Malignant transformation of neurilemmomas is exceedingly rare.
Kara Melissa T Torres, MD, DPDS, Visiting Research Fellow, Ackerman Academy of Dermatopathology
Disclosure: Nothing to disclose.
Coauthor(s)
Dirk M Elston, MD, Professor and Chairman, Department of Dermatology and Dermatologic Surgery, Medical University of South Carolina College of Medicine
Disclosure: Nothing to disclose.
Specialty Editors
Michael J Wells, MD, FAAD, Dermatologic/Mohs Surgeon, The Surgery Center at Plano Dermatology
Disclosure: Nothing to disclose.
Lester F Libow, MD, Dermatopathologist, South Texas Dermatopathology Laboratory
Disclosure: Nothing to disclose.
Chief Editor
Dirk M Elston, MD, Professor and Chairman, Department of Dermatology and Dermatologic Surgery, Medical University of South Carolina College of Medicine
Disclosure: Nothing to disclose.
Acknowledgements
Günter Burg, MD Professor and Chairman Emeritus, Department of Dermatology, University of Zürich School of Medicine; Delegate of The Foundation for Modern Teaching and Learning in Medicine Faculty of Medicine, University of Zürich, Switzerland
Günter Burg, MD is a member of the following medical societies: American Academy of Dermatology, American Dermatological Association, International Society for Dermatologic Surgery, North American Clinical Dermatologic Society, and Pacific Dermatologic Association
Disclosure: Nothing to disclose.
Grace F Kao, MD Clinical Professor of Dermatopathology, Department of Dermatology, University of Maryland School of Medicine and George Washington University Medical School; Director, Dermatopathology Section, Department of Pathology and Laboratory Medicine, Veterans Affairs Maryland Healthcare System, Baltimore, Maryland
Grace F Kao, MD is a member of the following medical societies: American Academy of Dermatology, American Society of Dermatopathology, and International Society of Dermatopathology
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.
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.
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.
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
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.
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.
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.
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.
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.
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.
Management algorithm for schwannoma nerve graft.
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.
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.
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
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.
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.
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.
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.
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.
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.
Solitary cutaneous plexiform neurilemoma shown on photomicrograph.
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