Abstract
A primary adenomatous tumor of the middle ear was examined by light microscopy, ultrastructural and immunohistochemical techniques. In support of its extensive neuroendocrine differentiation, was the diffuse detection of neuron-specific enolase (NSE) and positive im munoreaction with antibodies to chromogranin and synaptophysin. The great majority of tumor cells contained neurosecretory granules and intraluminal mucin production could be focally detected. These characteristics confirm the diagnosis of a middle ear adenomatous tumor (MEAT) of a biphasic nature and with a prominent neuroendocrine component.