Learning Objectives: Learning Objectives Middle ear adenomas are exceedingly rare Pre-operative radiological workup does not always correlate with intraoperative findings and clinicians should keep an open mind Histological classification of middle ear adenomas remains controversial Surgical resection is the treatment of choice.

Introduction: Middle ear adenoma is a rare differential diagnosis for a middle ear mass. Histological classification of middle ear adenomas remains poorly defined. As well as presenting our experience of one such case, this study aims to assimilate findings from previously published cases in order to contribute to our knowledge of a rare diagnosis.

Method: We report the case of a 51 year old male who presented with symmetrical tinnitus and left sided hearing loss. Examination revealed a postero-inferior mass behind the left tympanic membrane. CT and MR imaging was consistent with a tumour arising from the chorda tympani nerve and a pre-operative diagnosis of chorda tympani neuroma was made. However, intra-operative findings revealed a well-defined mass, close to but distinct from the chorda tympani nerve. Histopathology of the tumour was consistent with a middle ear adenoma.

Results: A review of the literature shows 95 previous reported cases of middle ear adenoma with the entity first described in 1976. A common theme is the difficulty of making a correct pre-operative diagnosis when faced with a middle ear mass, despite modern imaging techniques. Histologically, middle ear adenomas continue to defy classification with their cell line of origin posing the main point of controversy: exocrine versus neuroendocrine cell types. This in turn poses controversies regarding treatment and follow up.

Conclusion: Middle ear adenomas are rare. Reported cases highlight the difficulty of interpreting preoperative imaging. The histological classification of these tumours poses a further difficulty. With the natural progression and prognosis if left untreated of these tumours remaining unknown, further studies and reports would be a welcome addition to the literature. A current literature review advocates a radiological workup and surgical excision where there is clinical suspicion of middle ear adenoma