Middle ear adenoma. A cytologically uniform neoplasm displaying a variety of architectural patterns.

Seven patients with middle ear adenomas (MEA) are presented. MEA are cytologically stereotyped neoplasms with a spectrum of architectural patterns. All tumors were composed of uniform, round, or ovoid cells that resembled normal middle ear epithelium. The histologic patterns varied from tumor to tumor and within a single lesion. Broad sheets of tightly packed cells were commonly present, but glandular and cribriform areas were also frequent. Complex, interdigitating trabeculae, rows of individual cells, and dissociated cells were sometimes seen. Grimelius argyrophil stains were focally positive in three of five stained tumors, but Churukian-Schenk argyrophil preparations demonstrated only rare positive cells in two of these cases. Lysozyme was demonstrable immunohistochemically in each tumor. Lysozyme is present in normal middle ear epithelium and may be a useful marker for MEA, since the tumor is apparently derived from these cells. The clinical features of the seven cases that we report are combined with 44 MEA from the literature. MEA seldom recurs after excision and very rarely invades bone. No patient died of disease. The clinical and histologic distinction of these tumors from plasmacytoma, paraganglioma, ceruminoma, carcinoid tumor, and papillary carcinoma is discussed.