Advanced stage adenoid cystic carcinoma of the sinonasal cavity and skull base: a retrospective 20-year analysis.

The purpose was to describe the presentation, treatment, and outcomes of skull base invasive sinonasal adenoid cystic carcinoma (SNACC). A retrospective cohort study was performed of all consecutive patients aged >18 years at the time of presentation, who were diagnosed as having primary SNACC with skull base invasion, at a single tertiary referral center between 2002-2022. Eighteen patients were enrolled (11 female, 7 male; mean ± standard deviation age at initial presentation 55 ± 14 years). Nasal obstruction was the most prevalent sign/symptom, followed by facial numbness, facial swelling, epistaxis and facial pain. The most common tumor epicenter was the maxillary sinus, followed by nasal cavity and ethmoidal sinuses. Middle fossa was invaded in 13 cases and anterior fossa in eight. Orbital invasion was evident in eight patients. Positive surgical margins were identified macroscopically in five patients and were not associated with worse overall survival (OS) (P = 0.356) or disease-specific survival (DSS) (P = 0.732). Perineural invasion was associated with reduced OS (P = 0.037) and DSS (P = 0.044). SNACC is a slowly progressing, rare entity that is usually at an advanced stage at diagnosis. Orbit and skull base invasion is common, necessitating destructive surgery with frequent free flap reconstruction. Perineural invasion is common and associated with reduced overall survival.