Middle ear adenoma (MEA) is not commonly encountered in clinical practice. Most patients have non-specific symptoms, such as conductive hearing loss or ear fullness. Due to the rarity of the tumor, there is scarce literature on this tumor, and its classification is still under debate. In this report, we present three cases of MEA who visited Osaka University Hospital during the last 5 years. In the first case, the patient presented with otorrhea, conductive hearing loss, and thickening of the ear drum. Biopsy of the ear drum failed to yield a diagnosis preoperatively. We performed tympanoplasty with mastoidectomy for tumor removal and diagnosis, and histopathological examination of the resected specimen revealed the diagnosis of MEA. The second case was initially diagnosed as having chronic otitis media and underwent tympanoplasty with mastoidectomy, but histopathological examination of the granulation-like tissue revealed the diagnosis of MEA. In both these cases, a second-look surgery was performed 6–7 months after the first one, which revealed local recurrences that were removed. In the third case, the tumor was localized in the posterior part of the tympanic cavity. Preoperative transtympanic biopsy revealed the diagnosis of MEA. En bloc resection of the tumor was performed by the transcanal approach. In all of these three cases, histopathological examination with HE staining and immunohistochemical staining for synaptophysin, neuron-specific enolase (NSE) and chromogranin-A revealed the diagnosis of adenoma of the middle ear. Treatment of MEA is, in principle, complete tumor resection; however, there is a high risk of residual disease and recurrence, and long-term follow-up is required. It is difficult to distinguish MEA from carcinoid tumors, which may also recur and metastasize. The Ki 67 index, which is often used as an indicator of malignancy in the field of gastroenteropancreatic neuroendocrine tumors, may help in guiding appropriate management.
