Carcinoid tumor of the middle ear cavity is a rare neoplasm of low malignant potential. It grows slowly and rarely metastasizes. We recently experienced a case of carcinoid tumor of the middle ear cavity occurring in a 51-year-old female who was presented with hearing loss and tinnitus of the right ear. A 1 cm sized pinkish soft mass was noted in the promontory of the middle ear. Histologically, the mass was composed of nests and cords of tumor cells with slightly pleomorphic nuclei and eosinophilic cytoplasm. The extracellular matrix was glassy pink, homogeneous and exhibited apple green birefringence under a polarized light microscope after Congo red staining. The tumor cells showed immunoreactivity for cytokeratin, chromogranin A, synaptophysin, neuron-specific enolase and calcitonin. Electron microscopic examination confirmed the presence of neurosecretory granules. The production of calcitonin and amyloid by the tumor cells suggests the possible relationship of this tumor to the thyroid C cells.ope
