Adenoid Cystic Carcinoma of Sphenoid Sinus with Dural Extension Misleading as Meningioma: A Case Report

Adenoid Cystic Carcinoma (ACC) of the salivary gland is very rare malignant tumour, accounting for less than 1% of the head and neck malignancies. It usually arises from the minor salivary gland present in the epithelium of the nasal cavity to paranasal sinuses. Females between 40 and 60 years of the age are usually affected. Intracranial extension of these tumours is extremely rare and often leads to misdiagnosis as brain tumours during initial evaluation. The present case was of a 33-year-old male who presented with complaints of reeling of head, headache, and blurring of vision in left eye for seven months. Magnetic Resonance Imaging (MRI) revealed a hypointense extra-axial dural-based lesion with calcification. The lesion extended into the left cavernous sinus, sphenoid sinus, and the wall of the nasopharynx. The patient underwent surgical excision based on radiological diagnosis of meningioma. Microscopic examination of the tumour tissue revealed basaloid tumour cells arranged in cribriform, acinar, and mucinous pattern. The tumour cells exhibited a high Nuclear-to-Cytoplasmic (N/C) ratio, scant cytoplasm, and hyperchromatic angulated nuclei. No evidence of meningothelial cells noticed in the examined sections. Based on these histomorphological findings, a diagnosis of ACC was made. Immunohistochemistry (IHC) was done to support the diagnosis. It remained positive for Pan-Cytokeratin (Pan-CK) and negative for p63. Given the rarity of ACC, its occurrence in sphenoid sinus with dural extension can mislead radiologist and clinicians into diagnosing meningioma, which led to an urge to presentation of this case.