|Year : 2014 | Volume
| Issue : 3 | Page : 160-162
A rare intraspinal tumor "ancient schwannoma" and diagnostic difficulty
Mithilesh Kumar Pandey, Omprakash Gupta, Debajit Ray Barman, Kaushik Roy, Parimal Tripathy
Department of Neurosurgery, Nil Ratan Sirkar Medical College and Hospital, Kolkata, West Bengal, India
|Date of Web Publication||7-Oct-2014|
Mithilesh Kumar Pandey
Department of Neurosurgery, Nil Ratan Sirkar Medical College and Hospital, Kolkata - 700 014, West Bengal
Source of Support: None, Conflict of Interest: None
Ancient schwannoma (AS) is a rare benign, encapsulated tumor with a slow growth rate. The symptoms are very few and non specific during early stage of disease, because of that, the diagnosis of AS is always a challenge. There is a tendency to confuse AS with malignant tumors on imaging and histology. Here we are reporting a case of AS of the dorsal spinal region at T8-T9 level in a 62 year male patient initially present with non specific right upper abdominal pain. Complete excision of tumour was done successfully, without intra-operative neurophysiological monitoring and microscope with a good postoperative neurological recovery.
Keywords: Ancient schwannoma, antoni A and antoni B cells, cystic schwannoma, intraspinal intradural tumor, schwannoma
|How to cite this article:|
Pandey MK, Gupta O, Barman DR, Roy K, Tripathy P. A rare intraspinal tumor "ancient schwannoma" and diagnostic difficulty. Saudi J Health Sci 2014;3:160-2
| Introduction|| |
Ancient schwannoma (AS), a rare variant of schwannoma was originally described by Ackerman and Taylor in 1951. When multiple degenerative changes are encountered, schwannoma fits into the category of AS which is extremely benign in course, with rare malignant transformation.  On cytology and histology these tumors have degenerative features, including nuclear atypia and hyperchromasia. Confusion with malignancy can be avoided by recognizing benign features such as absence of mitosis and preservation of spindle shape with large cohesive aggregates of cells. In this case report, the diagnosis of AS and its surgical technique were discussed.
| Case report|| |
The chief complaints of 62-years-old male was right upper abdominal pain that has been lasting for 2 yrs. Gradually progressing weakness with heaviness of both lower limbs was present for 3 months. Constricting band like sensation around the upper abdominal level, with numbness below that level was present for 3 months. Bladder and bowel incontinence was present for 3 months. Before presenting to neurosurgery department, he visited various departments and evaluated to search for the reason. In that process, ultrasonography (USG) and computed tomography (CT) scan of the abdomen was done several times. But nothing was found. Initial, the right. upper abdominal pain was described as non specific, poorly localized and later on mild to moderate in intensity, intermittent, sharp shooting and radiating type. There was no history of trauma, tuberculosis (TB) and diabetes mellitus (DM).
On neurological examination, there was spastic paraparesis with variable power loss 0/5-3/5 in both lower limbs. Below T-8 dermatomal level, loss of fine touch, impaired joint position sense and vibration sense were detected. Deep tendon reflexes of lower limb were exaggerated and superficial planter reflex extensor bilaterally. Local examination of spine was normal. Abdominal and other systemic examination were unremarkable. Neurocutaneous markers were absent.
MRI of the dorsal spine showed an intradural extramedullary lesion in right spinal canal at T8-T9 level, 12 mm in AP, 13 mm in transverse and 23 mm in cranio-caudal dimensions with heterogenous enhancement. The dorsal spinal cord was shifted towards left, side with intramedullary post compressive signal changes suggestive of cord edema [Figure 1]a-d.
|Figure 1: (a) Sagittal T1W MRI reveals hypo to isointense an intradural-extramedullary intraspinal tumor extending from T8-T9, (b) sagittal T2W MRI the lesion is hyperintense, (c) sagittal T1W MRI with Gd. contrast shows heterogenous enhancement, (d) axial T1W MRI with contrast at T8 level showing tumour originated from right side nerve root and displacement of spinal cord towards lt, (e) post operative sagittal T1W MRI with contrast is showing no residual tumor|
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The T8-T9 laminectomy with complete excision of tumor was done. The tumor was cystic in nature. The histopathological examination was reported as moderately cellular neoplastic lesion composed of spindle shaped cells in fascicles with areas of palisading of nuclei. Giant cells were present in fair numbers with areas of necrosis. Mitotic figures were absent. The final report was an AS [Figure 2]a and b. Postoperative dorsal spine MRI T1W contrast showed complete excision of tumour [Figure 1]e. Patient was followed-up for 2 years with good neurological recovery without recurrence.
|Figure 2: (a) Hematoxylin-eosin [×100] stained shows Antoni A (hypercellular) and Antoni B(hypocellular) cells characterised by spindle shaped cells in fascicles with areas of necrosis and absence of mitoses features suggestive of ancient schwannoma, (b) Hematoxylin-eosin [×400] Ancient schwannoma|
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| Discussion|| |
Schwannoma was arises from the embryonic neural crest cells of the nerve sheaths of peripheral and cranial nerves. It is a benign tumor of the peripheral nervous system, arising from Schwann cells. Schwannoma can occur virtually in any body location where peripheral or cranial nerves are present, and they correspond to 8% of primary intracranial and 29% of primary spinal tumours.  In the spinal region, schwannomas have a predilection for sensory nerves and tend to arise from the dorsal roots but occasionally, they may arise from the ventral motor root.  In our case it seems that the tumour was arising from dorsal root as the patient first symptom was non specific abdominal pain but later become radiating in dermatomal pattern. According to Russell and Rubenstein in 1971 these tumours emerge from the transformation of neuroectodermal pial cells into schwann cells, leading to a possible fast neoplastic growth of schwann cells located in "critical area" in the dorsal roots.
Delayed diagnosis is common because these tumours are slow growing, the surrounding anatomic environment is permissive, and the presenting symptoms are non-specific.  Symptoms are related to a slowly enlarging mass with pressure effects on nearby organs or sensory changes in the distributing area, of the affected nerve. 
The most common symptom is pain, either localized or radicular  as acute low back pain secondary to nerve root torsion  or traumatic intratumoural hemorrhage.  Even more rarely, they may present as non-specific abdominal pain.  As in our case, the patient presented initially with non specific abdominal pain and later changed to classical radicular pain, which led to delayed diagnosis.
Magnetic resonance imaging (MRI) is the preferred imaging modality; schwannomas generally have low-to-intermediate signal intensity on T1 and T2 weighted images. They may be heterogeneous with focal areas of hyperintensity and hypointensity, very high intensity regions seen on T2-weighted images correspond to cystic degeneration with surrounding collagenous fibrous tissue. With gadolinium contrast, the tumour is dense and heterogeneous, though smaller lesions may be homogeneous in particular; rim enhancement of an intradural extramedullary tumour suggests the diagnosis of schwannoma. 
Histopathological examination remains the mainstay of differentiation as clinico-radiographic features can be indistinguishable, the histological stains show two types of tissues: Antoni A and Antoni B. Nuclear palisading and associated Verocay bodies, which may reflect their prominent extracellular matrix and secretion of laminin are the dominant characteristics of Type A tissue, where as a loose organization with myxomatous and cystic changes that may represent degenerated Antoni A tissue are the main features of Type B. 
Sparse mitotic hyperchromatic nuclei and degenerative changes, such as cyst formation, calcification, with occasional sites of hemorrhage are the major histopathological characteristics of the ancient forms of schwannomas.  The cystic changes are likely to be attributable to mucinous degeneration, ischaemic necrosis, haemorrhage, and the formation of microcysts. 
The differential diagnosis of an ancient schwannoma or cystic schwannoma, includes cystic neurofibroma, ependymoma, epidermoid cyst, arachnoid cyst, cystic lymphangioma, cystic teratoma and cystic meningioma. 
AS, possibly behaves in a similar fashion to solid schwannoma, therefore the treatment of an AS is similar to other spinal schwannomas which involve radical surgical excision of the tumor and decompression of spinal nerves.  Surgical treatment of cystic schwannomas can be very challenging because of the adhesion of the tumor capsule to the surrounding structures, fragile tumor capsules, and difficulty in identifying the arachnoidal layer. Early identification of the arachnoidal planes without opening of the cyst and sharp dissection may be useful. 
Complete excision of tumour may prevent recurrence.  Hence complete excision without sacrificing nerve roots is feasible in most of the contained non-invasive varieties.  Prognosis is good and tumours do not typically recur, except in cases of neurofibromatosis-2 and schwannomatosis. 
In conclusion the AS is a rare benign tumor that can present with minimal non-specific symptoms that lead to delayed diagnosis. Radical tumour excision is the goal of treatment to prevent recurrence. Tumour was successfully removed even in resource-limited settings as long as the technical expertise is available.
| Acknowledgement|| |
Very much thanks to pathologist Dr Subir K. Dutta.
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[Figure 1], [Figure 2]