Adeno-carcinoid or amphicrine tumors of the middle ear a new entity?

The clinicopathological, ultrastructural and immunohistochemical characteristics of four primary tumors of the middle ear are reported. These neoplasms showed a striking, heterogeneous aspect ranging from solid-trabecular (Type I) to tubulo-glandular (Type II) growth patterns. Secretory activity of the tumor cells was evaluated by immunohistochemistry and electron microscopy. Based on these procedures, three cell types were found, mainly limited to tumors with a tubulo-glandular (Type II) growth pattern. Most frequent were B-cells with an abundant pale cytoplasm containing neuroendocrine granules, both cytokeratin and vimentin as well as several endocrine marker substances. Less frequent were A-cells, which are slender, darkly staining and line the glandular lumina. They showed exocrine activity only and stained strongly with a polyclonal cytokeratin antibody. Finally, least frequent were amphicrine cells, which were characterized by both lumina and neuroendocrine granules in their cytoplasm and were interpreted as the link between A and B cells. Although this morphological description closely resembles that of carcinoids and adenocarcinoids of the respiratory tract and gut, the clinical behaviour of these middle ear tumors nevertheless seems different, with no recurrence or metastasis after a follow-up of 1 to 14 years (median 78 months). Therefore, some authors suggest that these tumors should be classified as middle ear adenomas or adenomatous tumors. However, we strongly feel that these tumours represent a distinct entity and can be classified as adenocarcinoids or amphicrine tumors, i.e. demonstrating both exocrine and endocrine activities. Further work is required to evaluate the exact proportion of neuroendocrine and amphicrine tumors in the heterogeneous group of adenomas and in the rarely described group of adenocarcinomas.