Beyond the Skin: An Uncommon Presentation of Merkel Cell Carcinoma Involving the External Auditory Canal and Parotid Gland

Abstract

Merkel cell carcinoma (MCC) is a rare, aggressive neuroendocrine tumor found in elderly Caucasian patients arising from sun-exposed skin. It is associated with high rates of local invasion, distant metastasis, and recurrence. It has been associated with the Merkel cell polyomavirus (MCPyV) and immunohistochemical stains such as cytokeratin 7 (CK7). A rare case of infiltrative MCC involving the parotid gland and external auditory canal (EAC) is presented in a 73-year-old Caucasian female, who had presented to her family physician with two enlarging lesions noted in the left EAC and parotid gland. The diagnosis was confirmed through imaging features and immunohistochemistry. Despite the grave prognosis associated with metastatic MCC, the patient underwent a complete metabolic response to chemotherapy and is currently undergoing adjuvant radiotherapy. Given the rarity of this tumor and imaging findings consistent with a wide differential diagnosis, clinicians should have an index of suspicion for MCC with atypical features.