Parotid Mucoepidermoid Carcinoma Radiologically Mimicking a Benign Postauricular Epidermoid Cyst: A Case Report

Mucoepidermoid carcinoma of the parotid gland may occasionally present with cyst-like or deceptively benign radiologic features, even when the final histopathological architecture is predominantly solid. Diagnostic difficulty increases when the lesion appears separated from the parotid gland and mimics a superficial postauricular cyst.

We report the case of a 49-year-old patient presenting with a painful left postauricular swelling associated with ipsilateral House-Brackmann grade III peripheral facial paralysis. Ultrasound and MRI suggested a well-circumscribed benign cystic lesion, interpreted as a remodeled epidermoid cyst, located in the retroparotid/postauricular region. However, the clinical red flags prompted surgical management. Histopathological examination considered most compatible with a mucoepidermoid carcinoma involving the parotid/posterior parotid region, with dermal extension. The patient subsequently underwent total parotidectomy and cervical lymph node dissection, followed by adjuvant radiotherapy after multidisciplinary tumor board discussion.

This case highlights that any postauricular or parotid-region mass associated with facial nerve dysfunction should be considered malignant until proven otherwise, even when imaging suggests a benign cystic lesion. Radio-clinical discordance should prompt an oncologic diagnostic strategy and careful histopathological evaluation.