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

Background: 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. Case presentation: 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. Conclusion: 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.