Invasion of the hypoglossal nerve by adenoid cystic carcinoma of the tongue: case report and review of the literature.

Adenoid cystic carcinoma (ACC) is a rare but highly aggressive malignancy mainly originating from the salivary glands. ACC is well known for its propensity toward neural invasion (NI). NI is the process of neoplastic invasion in and along nerves. It is a distinct and well-documented phenomenon in ACC; however, it is an underestimated route of metastatic spread. Multiple distant metastases can be established through NI route, and NI is believed to portend a poor prognosis. Despite increasing recognition of NI in many malignancies, the molecular mechanism behind NI is not well established. We present a unique case of hypoglossal nerve invasion by ACC arising from the minor salivary glands in the tongue of a 34-year-old man. We also review and discuss current theories on the pathogenesis and mechanism of NI.