Introduction
Granular cell tumor is usually a benign soft tissue lesion of neural origin, first described in 1926 in the tongue. Immunohistochemistry and ultrastructural studies have identified GCT to originate from Schwann cells. It affects people over a wide range of age with a slight female preponderance and a peak incidence in the fourth to sixth decades of life. Head and neck regions are the most affected sites with over two third cases diagnosed in the tongue. GCT in the orbit is very rare.1, 2
Case Report
A 45 year old female came with complaints of forward protrusion of right eye and headache for 3 months. Patient was a known case of type 2 diabetes mellitus on treatment. General physical examination and systemic examination were insignificant. Vitals were stable on examination. Detailed ophthalmological examination was performed. Visual acuity with Snellen’s chart was 6/12+1 DSph 6/6 in right eye (RE) and 6/12+1Dcyl *150 6/6p in left eye (LE). Intraocular pressure with Goldmann applanation tonometry was 20 mmHg in both eyes. Colour vision with Ishihara pseudoisochromatic plates was found to be normal in both eyes. Contrast sensitivity with Pelli-Robson was found to be within normal limits in both eyes. Pupils 3 mm in both eyes and equally reacting to light. Orthoptics revealed Right divergent squint to alternate divergent squint, with exotropia of 60 prism diopters. In Worth four dot test BSV was absent. Extraocular movements in 9 gazes showed elevation restriction in the RE. Proptosis evaluation of the right eye revealed an axial proptosis with inferior scleral show and resistance to retropulsion with no corkscrewing of vessels. Hertel’s exophthalmometry with a baseline of 101 showed RE-23 mm and LE 20 mm. Fundus examination by indirect ophthalmoscopy revealed mild temporal pallor in both eyes. A provisional diagnosis of right orbital mass under evaluation was made and proceeded with investigations. B scan ultrasound with 10 MHZ in the RE showed a well defined encapsulated lesion measuring 2*1.6 cm filled with moderate intense echoes abutting the optic nerve in the inferior quadrant. No calcification was noted. Routine Blood work up was within normal limits. MRI orbit showed a well defined T1/T2/FLAIR hypointense lesion in the infero-lateral aspect of intraconal compartment of right orbit showing mild restricted diffusion. The lesion was found to compress the inferior rectus muscle with mild displacement of the optic nerve superomedially. The lesion also showed moderate homogenous enhancement with intravenous contrast with no adjacent bony erosion. After obtaining anesthetic fitness, under general anesthesia, by inferior transconjunctival orbitotomy, total excision of the intraconal lesion was done and sent for HPE. HPE under low power microscopy revealed a mass composed of round to polygonal cells with abundant eosinophilic cytoplasm with eosinophilic cytoplasmic granules and centrally placed round nuclei. The stroma showed focal lymphoid aggregates suggestive of GCT. Specimen was sent for IHC for confirmation of diagnosis. Immunohistochemistry showed S-100-diffuse positive in 100% tumor cells and CD-68 positive in 100% tumor cells in favor of GCT. Postoperatively patient was started on IV antibiotics, tablet prednisolone 30 mg once daily and topical antibiotic eye drops. Patient did well in the postoperative period and was asked to review weekly at ophthalmology outpatient department.
Figure 5
Well defined encapsulated lesion of size 2x1.6 cm filled with moderate reflective echoes abutting optic nerve in inferior quadrant
Discussion
GCT is a benign soft tissue lesion. Malignant GCTs are extremely rare, accounting for less than 2% of all GCTs.3, 1 It was first described by Abrikossoff in 1926 as a granular cell myoblastoma in the tongue and was thought to originate from mature striated muscle cells.4 Later, GCTs were found to be of neural origin according to various histochemical and ultrastructure studies. Most patients are middle-aged, with a peak incidence in the fourth through the sixth decades of life. A slight female predominance exists, with an estimated female-to-male ratio of approximately 3:2. According to studies, up to 10% of granular cell tumors are multiple5 and 10 to 15 % of GCTs were found to be multicentric. A review by Ordóñez and Mackay6 concluded that GCT is most frequently located in the head and neck area and that about one-fourth of the lesions occurred in the tongue. Other reported sites are the larynx, parotids, breast, esophagus, respiratory, gastrointestinal, and genitourinary tract7 In ocular adnexa,8 GCT has been reported to occur in the orbit, extraocular muscles, caruncle, eyelid skin, palpebral conjunctiva, and lacrimal drainage apparatus2 and furthermore GCT in the orbit was found to be rare. The most common complaints of orbital GCT patients are diplopia, proptosis, and restriction of mobility1 Malignant orbital GCT was scarcely reported. For determining the malignancy of the tumor as early as possible and to avoid metastasis, histological specimen examination and the rate of tumor progress can be two indicative parameters.9 A slowly developing tumor can be suggestive of a benign tumor and a majority of GCTs are usually benign. Immunohistochemistry and ultrastructural studies have identified GCT to originate from Schwann cells.10 In histology, GCT cells feature acidophilic granular cytoplasm packed with lysosomes.
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