Mucoepidermoid carcinoma masked by adjacent benign neural lesion: a case report

Introduction Mucoepidermoid carcinomas demonstrate a heterogeneous clinical presentation, occasionally mimicking other lesions (such as mucocele in the oral cavity). We present an unusual case arising in the parotid gland, masked by a neuroma. Clinical Presentation A 25-year-old female patient presented to neurology with left facial muscle twitching of 7 years duration, following chemotherapy for Hodgkin lymphoma. Clinical examination revealed muscle fasciculations under the left eye, nose, and angle of mouth. Cranial nerve examination and vision tests were otherwise normal. Magnetic resonance imaging revealed a lesion affecting the extracranial portion of the left facial nerve, with an adjacent parotid gland abnormality, determined as Schwannoma. The patient returned at age 28 with worsening facial weakness, and new magnetic resonance imaging revealed extension of the lesion through the stylomastoid foramen. Following further deterioration of facial muscle function, the lesion was resected with a facial nerve graft. Histopathology Sections revealed a well-circumscribed nodule of neural tissue demonstrating direct intraneural infiltration by islands of a cystic epithelial tumor lined by bland cuboidal/columnar epithelium with occasional clear, mucous and intermediate cell types. ABPAS staining confirmed the presence of mucin. The features were of a neuroma infiltrated by mucoepidermoid carcinoma. Outcome Following multidisciplinary tumor board discussion, the patient will undergo temporal bone resection, radical parotidectomy, and selective neck dissection. Further outcome will be presented. Conclusions Mucoepidermoid carcinomas are the most common salivary malignancies. Our case report highlights that these tumors can show a wide variety of presentation depending on site and size. In this case an adjacent pathology, albeit benign, confused the clinical picture.