Primary adenomatous neoplasms of the middle ear: light and electron microscopic features of a group distinct from the ceruminomas.

The light and electron microscopic features of two primary adenomatous neoplasms of the middle ear are presented and compared with those cases in the literature. Primary adenomatous neoplasms of the middle ear appear to be derived from the lining epithelium of the middle ear and are distinct from the cercuminomas. They exhibit benign or indolently malignant behavior. Cytologic and histologic features are bland and uniform. Invasion of adjacent soft tissues and/or bone is the only histologic feature indicative of malignancy. Distant metastasis has not been reported. The duration and nature of the symptoms are of little diagnostic value. Radiographic and/or operative evidence of bone erosion reflects the aggressive potential of these neoplasms, although its absence does not exclude microscopic invasion. The primary adenomatous neoplasms of the middle ear recur locally if incompletely excised. Radical mastoidectomies and/or complete removal through the external auditory canal are curative.