Right Ethmoidal Sinus Schwannoma: Case Report of a Common Entity with an Unusual Presentation

Schwannomas are benign, encapsulated nerve sheath tumors arising from Schwann cells. Approximately, 25-40% of all Schwannomas occur in the head and neck region, acoustic nerve being the most frequent site. The tumors originating from nasal cavity or paranasal sinuses are rare and constitutes only four percent. A 40-year-old male presented with history of blurred vision of right eye and protrusion of right eye ball since 6 months. It was associated with history of watering and redness. Examination of right eye revealed mild proptosis and ptosis. Computed Tomography [CT] scan showed a large expansile cystic lesion measuring about 5.2x5.6x6.5cm involving entire right ethmoidal sinus. It showed expansion into anterior cranial fossa, roof and medial wall of right orbit. Radiological opinion suggested mucocele of right ethmoidal sinus. Intra-operatively, tissue specimen was sent for squash smear cytology. Cytology smears showed features suggestive of spindle cell tumor. Possibility of Schwannoma was considered. The specimen was subsequently subjected to histopathological examination. Microscopy showed tumor tissue composed of tumor cells arranged in alternate hypercellular and hypocellular pattern. Hypercellular areas showed occasional verocay bodies. Hypocellular areas showed loosely arranged spindle shaped tumor cells. Histopathological features were suggestive of Schwannoma. On Immunohistochemistry (IHC), neoplastic cells were positive for S-100 and negative for EMA. Ethmoidal sinus schwannoma extending into anterior cranial fossa is an unusual presentation. Clinically, it poses a diagnostic dilemma. Squash smear cytology is challenging, but helpful in establishing the correct diagnosis. Histopathology is confirmatory and immunohistochemistry is supportive.