Unknown primary mucoepidermoid carcinoma: diagnosis and treatment.

BACKGROUND Mucoepidermoid carcinoma (MEC) is the most common malignant salivary gland tumor. The majority of MECs occur in major or intraoral minor salivary glands. Herein, we present a case of MEC metastatic to cervical lymph nodes with an unknown primary site and discuss diagnostic and treatment options. METHODS AND RESULTS The patient was a 43-year-old man who presented with a large right-sided neck mass. Excisional biopsy demonstrated MEC involving multiple lymph nodes. Subsequent positron emission tomography (PET)/CT and multiple biopsies of potential primary sites failed to localize the primary tumor. The patient was treated with radiation to the ipsilateral neck and parotid/submandibular glands and has no evidence of disease 1 year after completion of treatment. CONCLUSION MEC presenting as cervical lymph node metastasis with an undiagnosed primary site is extremely rare. We report results of our literature review and provide a rationale for our experience in treating unknown primary MEC.