Middle ear adenoma can be a rare cause of a middle ear mass. These benign tumors can have epithelial and/or neuroendocrine differentiation. In 1976, Hyams was the first to describe a series of these tumors. It is still thought that these tumors are indistinguishable in composition from each other. We report a case of middle ear adenoma, the clinical and pathologic findings of which illustrate the biological behavior of the middle ear. A 17-year-old male presented with a history of recurrent, bloody otorrhea and high-pitched tinnitus. We diagnosed him with congenital cholesteatoma and performed surgery to remove the entire tumor as well as the incus. However, on postoperative pathology examination, we finally diagnosed the tumor as middle-ear adenoma with neuroendocrine differentiation. In the two years following surgery, the patient's adenoma has not recurred, although long-term observation will be required.