Endolymphatic sac tumor

An endolymphatic sac tumor is a very uncommon papillary epithelial neoplasm arising within the endolymphatic sac or endolymphatic duct. This tumor shows a very high association with von Hippel-Lindau syndrome (VHL).

This tumor has been referred to as adenocarcinoma of endolymphatic sac, Heffner tumor, papillary adenomatous tumor, aggressive papillary adenoma, invasive papillary cystadenoma, and papillary tumor of temporal bone. However, these names are not encouraged as they do not accurately classify the current understanding of the tumor.

Most patients present clinically with progressive, one sided hearing loss, much more often of the sensorineural rather than conductive type. Patients may also experience tinnitus, vertigo, and loss of vestibular function (ataxia). Symptoms are usually present for a long time, which supports the slow growth of these tumors. Patients may also present with other symptoms related to von Hippel-Lindau syndrome in other anatomic sites, which will result in imaging evaluation of the head.

Imaging studies help to identify the tumor and the specific anatomic site of involvement. Magnetic resonance images show a hyperintensity (hypervascularity) of a heterogeneous mass by T1 weighted images. Computed tomography shows a multilocular, lytic destructive temporal bone mass, centered within the endolymphatic sac (between internal auditory canal and sigmoid sinus).

The von Hippel-Lindau tumor suppressor gene generally has a germline mutation. This suppressor gene is also called elongin binding protein and G7 protein. The VHL protein is involved in up-regulation of hypoxic response via the [[hypoxia inducible factor [HIF]-1 alpha]]. Mutations generally prevent the production of any functional VHL protein or result in a change of structure of VHL protein. This genetic disorder shows an autosomal dominant inheritance pattern, with about 20% of patients possessing a new mutation. There are usually several other tumors which are part of the syndrome, including tumors of the central nervous system, kidneys, pancreas, adrenal glands, epididymis, broad ligament, along with the endolymphatic sac. The vast majority of patients with an endolymphatic sac tumor have von Hippel-Lindau syndrome.

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