[Amphicrine adenoma of the middle ear. Histological, immunohistochemical and ultrastructural study of a case].

Middle ear adenoma is a rare benign tumor that exhibits a pleomorphic histological pattern, with solid, cribriform, tubular and trabecular features, which often lead to a diagnosis of a malignant tumor. We report a case of middle ear adenoma, displaying the typical amphicrine biphasic cell growth, better visualized by immunohistochemical and ultrastructural studies. These tumors are composed of two cell types, endocrine B cells containing neurosecretory granules and labelled with anti-keratin, anti-vimentin and anti-neuron specific enolase antibodies, and exocrine A cells containing mucous granules and immunoreactive with anti-keratin and anti-epithelial membrane antigen antibodies. These immunohistochemical and/or ultrastructural characteristics may be helpful to confirm the diagnosis of middle ear adenoma which should be treated by local excision without additional therapy. The essential identity of middle ear adenoma and so called carcinoid tumors of the middle ear is highlighted. We propose to name these tumors middle ear amphicrine adenoma which better reflects their benign and biphasic nature.