Metastatic Salivary Ductal Carcinoma to the Mastoid Segment of the Facial Nerve

OBJECTIVE: To describe salivary ductal carcinoma (SDC) presenting as an isolated lesion of the mastoid segment of the facial nerve PATIENTS:: A 70-year-old man presenting with weakness of his right lower lip that progressed to complete facial paralysis over a span of 2 weeks. MAIN OUTCOME MEASURES: Clinical case records, immunohistochemical analyses, and radiological analyses including magnetic resonance imaging and positron emission tomography-computed tomography. RESULTS: Nodular enhancement along the mastoid segment of the facial nerve was identified without any mass within the parotid on magnetic resonance imaging or regional/distant disease on positron emission tomography-computed tomography. Pathologic analysis of tissue obtained from a right parotidectomy, neck dissection, and transmastoid resection of the vertical segment of the facial nerve revealed a benign parotid gland with malignant glands identified intra- and perineurally within the central aspect of the gland. CONCLUSIONS: SDC is one of the most aggressive salivary malignancies and typically presents as a rapidly enlarging mass in the involved gland. Although SDC's clinical course is characterized by early metastasis, isolated neural invasion has not been reported in the absence of an identifiable primary tumor within the gland of origin. The present case illustrates the clinical history and treatment of the first case of a SDC presenting as an isolated facial nerve lesion from perineural spread.