Endolymphatic sac tumours.

This review article surveys clinical and pathological literature on endolymphatic sac tumours (ELST) and summarizes characteristics that describe the entity. ELST are rare neuroectodermal neoplasms in the petrous bone, originating from inner ear structures. They can be encountered sporadically or in von Hippel-Lindau disease. The most prominent symptom is sensorineural deafness. Historically, nomenclature of invasive adenoid tumours in the petrous bone has been divergent, the term papillary adenocarcinoma used most frequently. Histologically, they have a follicular or papillary and adenoid pattern that can be easily confused with various other neoplastic conditions including metastatic carcinoma. It remains to be verified whether similar tumours (papillary adenocarcinomas) can originate from the middle ear. Middle ear adenomas have a similar appearance but probably originate from neural crest cells in the middle ear. ELST can express a variety of epitopes (including cytokeratin and neuroectodermal markers) which can be detected immunohistochemically. In cases in von Hippel-Lindau disease the cerebello-pontine angle should be included in routine radiological examinations to detect ELST before the tumours lead to deafness. In apparently sporadic cases of ELST, genetic testing for von Hippel-Lindau disease should be considered. Correct distinction of ELST from metastatic carcinoma prevents futile searches for unknown primary tumours.