Incidental Mucoepidermoid Carcinoma of the Accessory Parotid Gland in a Child: A Case Report

Background Mucoepidermoid carcinoma (MEC) of the accessory parotid gland (APG) is exceedingly rare in children: only five cases have been reported individually. APG tumors are nonetheless malignant in approximately 24% to 39% of cases and are closely related to the buccal branches of the facial nerve. We describe a sixth case, to our knowledge the first excised as a presumed benign cyst and then re-excised through a combined pre-auricular and trans-facial approach in a previously violated field. Case presentation A 9-year-old boy presented with a 4-month left cheek mass. MRI demonstrated a thick-walled cystic lesion in the APG territory, interpreted as a mucous retention cyst, and excisional biopsy was undertaken on that basis. Histopathology and immunohistochemistry confirmed intermediate-grade MEC with positive margins. At definitive re-excision, a pre-auricular incision first permitted identification of the facial nerve in unoperated tissue; the scar and tumor bed were then excised en bloc through a trans-facial extension, down to the preserved parotid duct. Two small residual foci were excised with a close (<1 mm) deep margin and clear remaining margins. After multidisciplinary discussion, surveillance was preferred to radiotherapy. At 13 months, the patient was disease-free, with House-Brackmann grade I facial nerve function. Conclusion A mid-cheek mass in the APG territory in a child warrants cytology and assessment by a surgeon experienced in parotid and facial nerve surgery before any incision, however reassuring the imaging. Where revision surgery is needed in a violated field, this combined approach may permit oncological resection with facial nerve preservation.