Granular Cell Tumor of the Orbit
A 50-year-old woman presented with a 4-year history of vertical diplopia and painless superior displacement of the right eye. She had no history of ocular discharge or thyroid eye disease. Biopsy of the right orbital mass three years before had yielded a non-specific diagnosis.\nOn admission, best corrected visual acuity (BCVA) was 20/30 and 20/20 in the right and left eyes, respectively; a mild afferent pupillary defect was also noted in the right eye. There was a firm non-tender mass palpable through the right lower lid producing a small amount of proptosis and upward displacement. Exophthalmometric values were 18 mm and 14 mm on the right and left sides, respectively (). A significant reduction in ocular abduction and depression was noted without orbital bruits or pulsation. Slit lamp biomicroscopic examination was unremarkable but funduscopy disclosed right optic disc swelling nasally. Ishihara test revealed red-green color deficiency and visual field testing demonstrated a cecocentral scotoma in the right eye. Intraocular pressure was 15 mmHg bilaterally.\nOrbital computed tomography (CT) scan showed enlargement of the right inferior rectus muscle which was infiltrated by a muscle-density mass displacing the globe upward; maxillary sinus involvement and bone erosions were not observed ().\nDue to close proximity of the tumor with inferior orbital muscles, a subciliary approach was employed to excise the tumor. Under general anesthesia, the anterior portion of the mass was excised as much as possible and sent in 10% formalin solution for histopathologic evaluation. Complete excision of the mass was not feasible due to infiltration of the tumor within the rectus muscle and other orbital structures.\nGross examination revealed a cream-colored to brownish firm mass measuring 20Í16Í12mm. After tissue processing and embedding in paraffin blocks, thin sections were stained with hematoxylin and eosin (H&E) and periodic acid-Schiff (PAS). Microscopic examination disclosed a partially encapsulated mass composed of lobules and cords of polyhedral and spindle-shaped cells with bland nuclei and intracytoplasmic PAS-reactive granules (A and B); however, mitosis was not a feature. The tumor cells were strongly immunoreactive for S100 in both nuclear and cytoplasmic areas but not for HMB45 and pan-cytokeratin immunostaining (C and D). These histopathologic features were consistent with GCT.\nDuring a six-month postoperative course, BCVA of the right eye decreased gradually and multiple sessions of radiotherapy, summing to 40 Gy in 2 Gy fractions, failed to control the growth of the residual tumor. Eventually vision dropped to no light perception and exenteration of the right orbit was performed to prevent extension of the tumor to the optic canal.