Slowly progressive facial paralysis: Intraneural squamous cell carcinoma of unknown primary

Background In this report, we present a unique case of intraneural squamous cell carcinoma of unknown primary found within the facial nerve and the proposed algorithms for diagnosis and management of progressive idiopathic facial paralysis. Case presentation A 66-year-old female with a previous history of basal cell carcinoma presented with right-sided progressive facial paralysis. Repeated magnetic resonance imaging as well as targeted workup failed to reveal a diagnosis. 20 months following symptom onset, after the patient's facial function slowly progressed to a complete paralysis, repeat magnetic resonance imaging revealed enhancement at the stylomastoid foramen. The patient underwent superficial parotidectomy, transmastoid facial nerve decompression and resection of descending and proximal extratemporal facial nerve segments, as well as great auricular nerve interposition grafting. Intraoperatively, frozen sections from the surface of the facial nerve, and the proximal and distal segments of the facial nerve following resection, were negative for malignancy. The final pathology revealed infiltrating poorly differentiated squamous cell carcinoma of the facial nerve with negative margins. Conclusion In cases of slowly progressive facial paralysis the clinician needs to consider malignancy until proven otherwise. Without an identifiable primary malignancy, early algorithmic assessment of presenting characteristics may facilitate expedited clinical decision making and surgical management of malignancy involving the facial nerve. In cases of slowly progressive facial paralysis, when the time comes for surgical exploration and biopsy, head and neck surgeons must be aware that malignancy can exist entirely within the facial nerve, without pathologic changes on the surface of the nerve or in the surrounding tissue.