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| Year : 2013 | Volume
: 24
| Issue : 6 | Page : 768-771 |
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| Unusually large quiescent ancient schwannoma of hypoglossal nerve |
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Sangeeta P Wanjari1, Panjab V Wanjari2, Rajkumar N Parwani1, Satyajitraje A Tekade1
1 Department of Oral and Maxillofacial Pathology, Modern Dental College and Research Centre, Indore, Madhya Pradesh, India
2 Department of Oral Medicine and Maxillofacial Radiology, Modern Dental College and Research Centre, Indore, Madhya Pradesh, India
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| Date of Submission | 16-Feb-2013 |
| Date of Decision | 19-Mar-2013 |
| Date of Acceptance | 17-Apr-2013 |
| Date of Web Publication | 20-Feb-2014 |
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 Abstract | | |
Ancient schwannoma is considered as a variant of schwannoma, comprising about 10% of all schwanommas. Schwannoma is a benign neoplasm derived from the nerve sheath of peripheral motor, sensory and sympathetic nerves and from the cranial nerve pairs. It usually presents as a solitary soft-tissue lesion which is slow growing, encapsulated and is often associated with nerve attached peripherally. Diagnosis is often confirmed with the microscopic examination. The long standing schwannoma attributes to degenerative changes and is termed "ancient" schwannoma. Present case is of a 68-year-old female patient who reported with an asymptomatic large swelling below mandible on the left side since last 23 years. The lesion was surgically excised under general anesthesia. Keywords: Ancient schwannoma, hypoglossal nerve, verocay bodies
How to cite this article:
Wanjari SP, Wanjari PV, Parwani RN, Tekade SA. Unusually large quiescent ancient schwannoma of hypoglossal nerve. Indian J Dent Res 2013;24:768-71 |
How to cite this URL:
Wanjari SP, Wanjari PV, Parwani RN, Tekade SA. Unusually large quiescent ancient schwannoma of hypoglossal nerve. Indian J Dent Res [serial online] 2013 [cited 2023 Jun 9];24:768-71. Available from: https://www.ijdr.in/text.asp?2013/24/6/768/127632 |
Schwannoma described by Theodor Schwann, also named as neurilemmoma by Stout; is an uncommon, solitary, benign, soft-tissue or intrabony neurogenic slow growing tumour that arises from the neural crest. [1],[2],[3] It develops from schwann cells of nerve sheath of peripheral motor, sensory and sympathetic nerves and from the cranial nerve pairs, with the exception of the optic and olfactory nerves that do not have a schwann cell sheath. [3],[4],[5] Locating the nerve of origin is difficult and only 50% cases can be correlated with the nerve of origin. Pre-operative diagnosis of these lesions is rare. [3] Five histological variants of schwannomas have been described by Weiss and Goldblum as: Common, plexiform, cellular, epithelioid, and ancient. [5],[6]
Ackerman and Taylor (1951) reviewed 48 cases of thoracic tumors of neurogenic origin and found 10 cases which showed the features consistent with common schwannoma, with distinctive areas of hypocellular tissue. Furthermore, they attributed these features to long-standing degenerative alterations and coined the term "ancient" for such type of benign neurogenic tumor. Ancient schwannoma has been described in a variety of locations including oral cavity and head-neck region. [7]
| Case Report | |  |
A 68-year-old female presented with an asymptomatic swelling below the left lower jaw since last 23 years, which was initially smaller in size and slowly reached the present size. She was a known case of trigeminal neuralgia of the maxillary division on the left side since last 2 years and was under medication. Her routine laboratory findings were within normal range.
Extraoral examination revealed a single well-circumscribed swelling of size approximately 7.5 cm × 4.5 cm × 4 cm, oval in shape below the body and angle of the mandible on the left side. Anteroposteriorly, it had extended from left parasymphysis region to 1 cm distal to angle of mandible on the same side. Supero-inferiorly the lesion was located just below the lower border of mandible to 4 cm inferiorly [Figure 1].
On palpation, it was non-tender, non-pulsatile, soft to firm in consistency, freely movable, with normal temperature of the overlying skin. Ultrasonography revealed a large single hypoechoic mass measuring 70 mm × 40 mm × 40 mm adjacent to the left mandible, with a clear border between the surrounding soft-tissue and the bone.
The provisional clinical diagnosis was dermoid or epidermoid cyst with differential diagnosis of fibroma, fibrolipoma, neurofibroma, schwannoma fibromyxoma or leiomyoma.
Under general anesthesia, a well-encapsulated soft-tissue mass was surgically removed, which easily popped out with slight finger pressure. In addition, a lesion was attached to a hypoglossal nerve. The resected specimen was processed for histopathological examination.
The specimen consisted of a well-circumscribed mass measuring 7.0 cm × 4.0 cm × 4.0 cm which appeared to be glistening, smooth, capsulated, and whitish-grey in color with some dark grey areas. The cut surface showed whole area to be filled with whitish brown dough like granular material with some solid and cystic areas, except for thin rim of firm solid tissue with slight thickening toward one end at the periphery.
Microscopic examination revealed an encapsulated richly vascular tumor showing solid cellular areas with some stromal hyalinization and few variables sized cystic spaces [Figure 2]. The cells revealed biphasic pattern of spindle cells with indistinct cytoplasm and twisted nuclei in bundles or fascicles, consistent with schwann cells with central eosinophilic acellular verocay bodies indicative of Antoni A pattern. However, in other areas less cellular disorderly arranged spindle shaped cells, suggestive of Antoni B pattern was evident [Figure 3]. In some areas, the tumor was infiltrated by numerous large histiocytes. Numerous dilated blood vessels of variable sizes were also observed some of which showed evidence of perivascular hyalinization while few were surrounded by histiocytes. Some hemorrhagic areas too were evident. Some areas revealed stromal hyalinization as well. Moreover, few atypical cells too were observed [Figure 4]. Strong positive and diffuse immunostaining was expressed by spindle shaped cells for S-100 protein [Figure 5]. All these histological features strongly directed toward the diagnosis as an ancient schwannoma. | Figure 2: Photomicrograph showing lesional tissue surrounded by capsule (H and E, ×100)
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 | Figure 3: Photomicrograph showing diffuse proliferation of tumor cells in Antoni-A and Antoni-B arrangement withVerocay bodies (H and E, ×150)
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 | Figure 4: Photomicrograph showing diffuse proliferation of tumor cells, dilated vessels,perivascular and stromal hyalinization, perivascular lipid laden histiocytes, few atypical cells (H and E, ×150)
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Five days post-operatively, patient complained of some difficulty in speech. Intraoral examination revealed deviation of tongue toward the left side on protrusion. Otherwise healing was uneventful. Periodic follow-up for 1 year at the interval of 3 months, revealed prognosis to be excellent with no recurrence of the lesion. However, until date no improvement was observed in deviation of tongue.
| Discussion | | |
The swannoma appears as a slow growing, sharply defined, solitary mass of variable size without neurologic symptoms, although on occasions it can compress the accompanying nerve as well as the neighboring structures, producing symptoms derived from the pressure such as pain and paresthesia. [3]
In 1985, Erlandson classified schwannomas into 7 subtypes: Classical (verocay), cellular, plexiform, cranial nerve, melanotic, degenerated (ancient), and granular cell. Classical and plexiform schwannomas often arise in superficial soft-tissues, particularly of the head and neck region, which is rich in superficially situated peripheral nerves. [8]
Oral swannomas exhibit two types: The common type, which appears as submucosal, well-defined, firm, encapsulated nodule resembles cyst and the other type appears to be non-encapsulated, where tumor is found below the basal layer of oral mucous membrane. [1] The present case simulates the features as 1 st type.
Approximately, 25-40% of all schwannomas occur in the head neck region, whilst ancient schwannoma rarely affects this region. [6],[7] Reviewing the literature, ancient schwannomas were mostly seen in females, [1],[8] so was true even in the present case. However, few studies state to show equal sex predilection. [2],[4] They may occur in association with neurofibromatosis type 2 or arise sporadically. [2] Present case too showed sporadic involvement.
Molecular pathogenesis for schwannoma formation and neurofibromatosis type 2 was explained as mutations in NF2 gene at position 22q12.2. It is a tumor suppressor gene that codes for merlin (schwannomin), a cell membrane associated protein that links the cell membrane and cytoskeleton and functions in intracellular signaling pathways. Its decreased synthesis causes a disturbance of growth arrest through cell-cell contact. [2]
Ancient schwannomas can vary from firm, solid masses to fluctuant cysts, which cannot be clinically distinguished from other types of schwanommas. The mean age of occurrence is 43.7 years with a range between 21 years to 65 years. [7] In general, this tumor is small and ranges between 0.3 cm and 3 cm, most being less than 5 cm, although, occasionally, it can grow until it reaches a diameter of 20 cm 2 . The present case showed a big sized lesion measuring 7.5 × 4.5 × 4 cm.
In the neck, vagus nerve is the most commonly involved nerve, followed by the cervical sympathetic nerve [9] while the tongue is the most common site of involvement intraorally. [10],[11] Moreover, in the present case, even though the lesion was located extraorally, the affected nerve was confirmed to be hypoglossal nerve, which is a motor nerve to almost all the muscles of tongue as post-operatively on protrusion tongue exhibited deviation toward the same side of the lesion. The Hypoglossal nerve after descending down to mandibular angle becomes superficial below the posterior belly of digastric. Then it inclines up and forward on hypoglossus, passes on to the lateral aspect of the genioglossus, further continues ahead in its substance and the muscular branch distributes its fibers in the muscles of tongue. [12] In the present case, the lesion was located superficial to digastric muscle in digastric triangle.
The schwannoma should be differentiated from the neurofibroma: A common neurogenic tumor that arises from the cells of nerve sheath. It is made up of a mixture of schwann cells and fibroblasts, and has a greater tendency of malignant transformation. The neurofibroma is generally non-encapsulated and lobulated tumor, with an irregular surface which gets intertwined with the nerve of origin; however, neurilemmoma pushes away the associated nerve. Neurofibroma is a tumor, which is difficult to remove, that recurs or persists when resection has been incomplete; and in cases of hereditary neurofibromatosis, it can transform into a malignant tumor. [3],[9] However, schwannomas rarely show malignant transformation that to in conventional form of all its variants. [2] Therefore, clinical and histological evaluation is necessary while dealing with neural tumors.
The only gold standard diagnostic investigation is histopathology of either incisional biopsy or excised specimen. [2] The predominant histopathological findings of ancient swannomas describes an encapsulated lesion with biphasic pattern with areas of highly ordered dense cellularity of spindle cells with verocay bodies suggestive of Antoni A pattern and less cellular, randomly arranged tumor cells suspended in a myxomatous matrix in Antoni B pattern. [2],[7],[13] Characteristically, this tumor is long-standing and may undergo degenerative "ancient" changes dominated by large cystic, myxoid areas with variable bizarre spindle cells and occasional mitosis, hemorrhage, hyalinization, calcification, large numbers of siderophages, and histiocytes. [7],[13] Degenerative atypical features may lead to an erroneous interpretation of malignancy. [2],[13] Present case revealed prominent histopathological features of both Antoni A and B arrangement with degenerative changes except calcification even though having a long standing history of 23 years. Immunohistochemical staining revealed strong diffuse positivity for S-100 protein, which is a precise way for diagnosis and classifying it as nerve sheath tumors. [3],[11]
Moreover, present case showed a coincidental association of trigeminal neuralgia, which started since 2 years for which she is under medical treatment. However, it did not show any relation with ancient schwannoma.
Complete surgical excision is the treatment of choice for these tumors. Cautious surgical treatment includes extracapsular "peeling" or even intracapsular enucleation of tumor from nerve, which can avoid transitory or permanent neurological sequela, for which information should be given to the patient. [10] However, prognosis is good without any reported recurrence or malignant transformation. [1]
| Conclusion | | |
Ancient schwannoma is uncommon in head and neck region. The etiology and natural history of schwannoma have not been properly characterized. It is a histological distinctive type of schwannoma. Although it is a benign tumor, atypical features of this tumor may lead to an erroneous impression of malignancy. Minimal or no mitotic figures and degenerative changes in typical cellular pattern aids in the diagnosis of ancient schwannoma. Complete surgical excision is the treatment of choice with an excellent prognosis. However, after removal of the neurilemmoma, transitory or permanent neurological sequela may appear, for which information should be given to the patient.
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Correspondence Address:
Sangeeta P Wanjari
Department of Oral and Maxillofacial Pathology, Modern Dental College and Research Centre, Indore, Madhya Pradesh
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/0970-9290.127632
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5] |
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