Salivary Duct Carcinoma Spread to the Internal Auditory Canal Along the Facial Nerve: A Case Report.

Salivary duct carcinoma (SDC) is a rare high-grade parotid malignancy prone to perineural spread. However, perineural spread of SDC has rarely been reported. The case of a 46-year-old male with SDC spread along the facial nerve (FN) is presented here. Despite their involvement, the FN geniculate ganglion and mastoid segment were ignored in the initial parotidectomy procedure. SDC progressed during the postoperative follow-up period, as clinicians were unaware of perineural spread. Finally, facial magnetic resonance imaging (MRI) and curved planar reformat (CPR)-computed tomography (CT) revealed involvement of the internal auditory canal (IAC) and the entire facial canal. In clinical practice, physicians should remain committed to recognizing the characteristics of SDC with FN invasion on facial MRI and CRP-CT, as both are valuable diagnostic tools and necessary to evaluate perineural spread along the FN.