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|LETTER TO EDITOR
|Year : 2017 | Volume
| Issue : 5 | Page : 1159-1161
Granular cell tumor at an unusual site masquerading as a neurofibroma
Irneet Mundi1, Ashis Pathak2, Ashru K Banerjee1, Rahat Brar3
1 Department of Laboratory Medicine, Fortis Hospital, Mohali, Punjab, India
2 Department of Neurosurgery, Fortis Hospital, Mohali, Punjab, India
3 Department of Radiology, Fortis Hospital, Mohali, Punjab, India
|Date of Web Publication||6-Sep-2017|
Department of Lab Medicine, Fortis Hospital, Phase 8, Mohali - 160 062, Punjab
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Mundi I, Pathak A, Banerjee AK, Brar R. Granular cell tumor at an unusual site masquerading as a neurofibroma. Neurol India 2017;65:1159-61
Granular cell tumor (GrCT) is rare and so named because of the classical histomorphology of the tumor cells having abundant granular eosinophilic cytoplasm. It most commonly occurs in the skin, head, and neck, with a particular predisposition for the tongue. Other common sites include the respiratory tract, breast, and gastrointestinal tract. GrCT of the spine is exceptionally rare and only 12 cases have been reported so far with only one case involving the S1 nerve. We report an unusual case of GrCT involving the S1 nerve root diagnosed as a neurofibroma on radiology.
A 21-year old female patient presented to the neurosurgery out-patient department with complaints of pain in the left leg for the last 1 month. The computed tomographic (CT) scan of the spine revealed a well-defined, dumbbell-shaped lesion measuring 19 × 19 × 34 mm within the left neural foramen at S1–S2 level with expansion of the neural foramen, which was diagnosed as a neurofibroma [Figure 1]. The findings were confirmed on magnetic resonance imaging (MRI), which showed an intensely enhancing lesion having a soft tissue attenuation, in the left S1 neural foramen along the course of the left S1 nerve root [Figure 2].
|Figure 1: Axial plain CT image in bone window setting showing a well-defined lobulated soft tissue attenuation lesion in the left S1 neural foramen, causing smooth expansion of the foramen without any bone destruction, suggesting a slow growing expansile lesion|
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|Figure 2: Sagittal T1-weighted contrast-enhanced MRI showing the intensely enhancing soft tissue attenuation lesion in the left S1 neural foramen along the course of the left S1 nerve root|
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The patient was operated in a prone position after verifying the level using a C-arm intensifier. A left-sided hemi-laminectomy was performed and the tumor was located on the left side with extension into the extraforaminal space. The tumor was moderately vascular, with a gritty outer layer and a soft inner core. The corresponding nerve root was seen merging imperceptibly with the capsule of the lesion. In order to avoid any neurological deficit, a good debulking of the tumor was done. No attempt was made to perform a total excision of the lesion. Postoperatively, the patient had no neurological deficit and her pain improved. The follow-up MRI showed a residual smaller lesion, which was planned to be followed up with interval imaging.
Light microscopy of hematoxylin and eosin-stained sections revealed a tumor comprising of round-to-polygonal cells. The cells had abundant granular eosinophilic cytoplasm and central small vesicular nucleus [Figure 3]. The granules were periodic acid Schiff (PAS) positive and diastase resistant [Figure 4]. On immunohistochemistry, the cells were diffusely positive for S-100 [Figure 4]. Ki-67 was 1–2%. No significant atypia, mitotic activity, or necrosis was noticed. Based on these findings, the lesion was diagnosed as a granular cell tumor.
|Figure 3: Photomicrograph showing tumor composed of cells having abundant eosinophilic granular cytoplasm (H and E, ×200)|
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|Figure 4: Tumor cells positive for S100 immunostain (×200). Inset: Cytoplasmic granules showing strong PAS positivity (PAS, ×400)|
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GrCTs were initially reported as granular cell myoblastoma in 1926 by Abrinkossoff, as they were considered to originate from smooth muscles. Recent studies using electron microscopy and immunohistochemistry have proven that these tumors exhibit schwannian differentiation. GrCTs of the nervous system are rare, and may arise from the peripheral nerves or the central nervous system (CNS). In the CNS, lesions have been reported in the cerebral hemispheres, cranial nerves, and spinal cord, but most often occur in the neurohypophysis or the infundibulum. Some authors propose that GrCTs arising in the neurohypophyseal region of the CNS may be of pituicytic origin. In contrast, cerebral hemispheric lesions tend to be positive for glial fibrillary acidic protein (GFAP), which, in addition to the ultrastructural features, is an indicator of the astrocytic origin of the tumor.
MRI, with and without contrast, is the imaging modality of choice for localizing this tumor. MRI findings suggest that GrCTs of the spinal cord are hypo- to isointense compared to the spinal cord on T1-weighted images, and can be slightly hyperintense on T2-weighted images. The tumor seems to enhance uniformly after contrast administration. These findings can be seen in other spinal canal tumors, including a schwannoma, neurofibroma, meningioma, paraganglioma, ependymoma, or metastatic tumor.,, A tissue biopsy is thus required for confirmation of diagnosis. Histopathologically, the tumors consist of large, rounded, polygonal, or elongated cells with well-defined to ill-defined cellular borders, giving a syncytial appearance. The cells have centrally or eccentrically located small, hyperchromatic-to-vesicular nuclei, enveloped by abundant, granular, eosinophilic cytoplasm. The cytoplasmic granules are PAS positive and diastase resistant. These cells are also strongly and diffusely immunoreactive with S-100 protein, CD68, neuron specific enolase, inhibin-α, protein gene product 9.5 (PGP9.5), and vimentin.,
Schwannoma is the most important differential diagnostic consideration at this site. Schwannomas have hypo- and hypercellular regions with formation of Verocay bodies. The cells tend to be spindled with wavy and elongated nuclei. Perivascular hyalinization can be prominent. Neurofibromas show wavy bundles of spindle-shaped cells in a myxoid matrix. Meningiomas show a whorled arrangement of cells with psammoma bodies. Cells of these three tumors lack cytoplasmic granularity seen in GrCTs.
Conventional GrCTs are benign neoplasms. Malignancy occurs in <2% of patients. Malignant changes are diagnosed by a combination of histological findings, including cellular pleomorphism, necrosis, and elevated mitotic activity. Clinical suspicion of malignancy should be higher if the lesion is large or growing rapidly, or if there is evidence of distant spread.
Conservative excision is the treatment of choice. Recurrence is seen in up to 7% of cases if they are incompletely resected. Radiation treatment has been used successfully to stabilize the recurrent disease.
To conclude, histological recognition of this rare tumor is important because radiologically, GrCT can mimic other tumors more commonly seen in this location; however, it has a different clinical course.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]