Middle ear adenoma is an amphicrine tumor: why call it adenoma?

Middle ear adenoma (MEA) is a rare tumor postulated to take origin from the lining epithelium of the middle ear cavity. The authors report on a case of MEA arising in a 53-year old woman suffering from a sensation of fullness in her left ear, otalgia, and light left-sided hearing loss. Histopathologically, the lesion was composed of cuboidal and polygonal cells displaying a trabecular, tubulo-glandular, and solid pattern of growth. Immunohistochemically, neoplastic cells diffusely stained with anti-vimentin antibodies and were focally positive for chromogranin A, neuron-specific enolase, lysozyme, and cytokeratins AE1/AE3. The majority of tumor cells showed weak and diffuse staining with both anti-PP and anti-ACTH antibodies and intense positivity with anti-glucagon and anti Leu-7 antibodies. Ultrastructural investigation revealed both mucinous-glandular and neuroendocrine differentiation. The authors suggest that the appropriate terminology would be adeno-carcinoid or amphicrine tumor of the middle ear rather than "adenoma," a term that does not reflect its dual nature.