Secondary Lower-Motor-Neuron Facial Palsy Revealing Buccal Squamous Cell Carcinoma with Parotid Duct Obstruction and Perineural Invasion.

Peripheral facial palsy is often attributed to idiopathic Bell's palsy, but secondary structural causes should be considered when local red flags are present. A 61-year-old man with a 40-pack-year smoking history and former betel quid chewing presented with a verrucous-appearing mass involving the left oral commissure and buccal mucosa, intermittent purulent discharge from the lesion, progressive left facial swelling, and ipsilateral lower-motor-neuron facial palsy with lagophthalmos. Magnetic resonance imaging demonstrated a left buccal/oral-cavity lesion with ipsilateral parotid duct obstruction. He underwent tracheostomy, wide excision, left supraomohyoid neck dissection, and radial forearm free-flap reconstruction. Pathology confirmed squamous cell carcinoma, pT2N0, cM0 (stage II), with perineural invasion; surgical margins were negative, and lymphovascular invasion was not identified. At follow-up, wound healing was satisfactory and purulent discharge had resolved, but lower-motor-neuron facial palsy persisted; adjuvant radiotherapy was recommended. This case emphasizes that lower-motor-neuron facial palsy with an oral mass, purulent discharge, facial swelling, or salivary-duct obstruction should prompt careful oral examination and head-and-neck imaging.