Nasopharyngeal Adenoid Cystic Carcinoma With Extension Into the Internal Auditory Canal: A Case Report

Adenoid cystic carcinoma (ACC) is a malignancy most commonly found in the major salivary glands. It can, however, arise from minor salivary glands throughout the upper aerodigestive tract. It is typically slow-growing and asymptomatic, though presentation varies with tumor location, pattern of infiltration, and degree of perineural invasion. ACC is characterized as an aggressive malignancy due to high rates of local recurrence and distant metastasis, with the lungs, bone, and liver commonly implicated. ACC spreading to the internal auditory canal (IAC) is highly unusual and has not been reported. We present the case of a 40 year-old male with no significant past medical history, found to have nasopharyngeal ACC that spread to the IAC resulting in multiple cranial neuropathies. The challenging location and complex path of spread along the skull base presented a significant barrier to surgery, though after completion of definitive radiation therapy, the patient experienced substantial reductions in mass effect and symptomatic relief. This report offers additional insight into the patterns of spread for ACC, emphasizing the importance of recognizing the IAC as a potential site of involvement. Early identification may significantly expedite management and prevent serious morbidities.