[Granular cell tumors of the orbit: diagnostics and therapeutic aspects exemplified by a case report]

Granular Cell Tumor of the Orbit: Review of the Literature and a Proposed Treatment Modality

PURPOSE

To document a unique case of granular cell tumor of the orbit, located lateral to and abutting the optic nerve, that benefited from treatment with proton beam irradiation, with a comprehensive review of the literature on granular cell tumor of the orbit.

METHODS

Clinicopathologic case report with detailed imaging features and histopathologic and immunohistochemical evaluation for cytoplasmic tumor biomarkers differentiating granular cell tumor (GCT) from it mimicking lesions with relevant literature citations. The authors reviewed 20 cases of orbital GCT from 2011 to 2020 in addition to 40 cases from 1948 to 2011 and included a summary of imaging and clinical features, outcomes, and recommended treatment modalities.

RESULTS

A 32-year-old man with 1-year history of left retrobulbar pain and diplopia on lateral gaze, intermittent left eyelid swelling, and a tonic left pupil was found to have a fusiform intraconal mass extending toward the orbital apex and abutting the optic nerve. Histopathologic and immunohistochemical investigations collectively supplied data diagnostic of a GCT with an initial low proliferation rate. GCT is a soft tissue neoplasm that originates in the nervous system and can occur anywhere in the body. This enhancing tumor is isointense to gray matter on T1-weighted MRI, hypointense on T2. After an incisional biopsy, the patient's symptoms persisted, and follow-up imaging several months later revealed further growth of the mass. The impossibility of complete surgical removal prompted the decision to treat with proton beam radiation therapy, which resulted in substantial regression in the size of the residual tumor. Most frequently involving the inferior rectus muscle (42%), orbital GCT is usually benign with only 4 reported cases of malignant orbital GCT (7%). Wide surgical resection with complete removal is usually curative for benign orbital GCT, and proton beam radiation therapy can aid in tumor shrinkage.

CONCLUSIONS

GCT should be considered in the differential diagnosis when encountering patients with mass lesions involving the extraocular muscles, peripheral nerves, or less frequently, the optic nerve or orbital apex. Immunohistochemical analysis of biopsied tissue is required for the definitive diagnosis of GCT. Consideration of adjuvant therapies such as proton beam radiation therapy may be appropriate in cases of incomplete surgical resection of benign GCT. Proton beam radiation therapy can be an excellent therapeutic option for symptomatic relief and residual tumor size reduction with an acceptable toxicity profile.

Rare Diseases of the Orbit

This article provides an overview of rare orbital diseases. Congenital malformations, inflammatory diseases, benign and malignant neoplasias are described. Although it represents a relatively small area of the body the orbit contains multiple different tissues. Therefore, a great variety of diseases can be found within the orbital space. That is the reason, why both the completeness and the level of detail in the description of particular diseases must be somewhat limited. Nevertheless, clinical manifestations, important aspects of diagnosis, treatment strategies, and, when specific data are available, the prognosis are described. The authors tried to highlight the most characteristic aspects of the different diseases to describe their relevant aspects in spite of the brevity of the subsections.

Surgical Excision of Orbital Progressive Granular Cell Tumour

Granular cell tumour (GCT) is mostly benign lesion first described by Abrikossoff and named after him. Most cases are reported in the head and neck area, where the tongue is the most common site. Here we review previous cases in the literature for GCT in the orbit and present a new case. A 49-year-old male presented with apparent exophthalmos. Examination of the patient revealed the presence of a mass in the bottom side of the orbit. A substantial progress was noted after two months from the initial examination using computed tomography (CT) scan. An orbital mass was extracted and histological analysis showed signs typical for GCT. Immunohistochemistry was positive for S-100; the biopsy showed no mitotic or necrotic areas. Proptosis was resolved after surgery and a six-year follow-up CT scan was performed. We conclude that rapid progress of the tumour does not necessarily suggest malignancy.