An endolymphatic sac tumor (ELST) 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). Classification
The ELST 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. Signs and symptoms
Patients with ELST may present clinically with progressive or fluctuating, one sided sensorineural hearing loss which may mimick Ménières disease due to the development of tumor associated endolymphatic hydrops. Patients may also experience tinnitus, vertigo, and loss of vestibular function (ataxia). Alternatively, symptom onset may be sudden, due to intralabyrinthine hemorrhage. 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 findings
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 on the vestibular aqueduct (between internal auditory canal and sigmoid sinus). Pathogenesis
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]].
From a pathology perspective, an endolymphatic sac tumor needs to be separated from metastatic renal cell carcinoma, metastatic thyroid papillary carcinoma, middle ear adenoma, paraganglioma, choroid plexus papilloma, middle ear adenocarcinoma, and ceruminous adenoma. Management
Wide excision is the treatment of choice, although attempting to preserve hearing. Based on the anatomic site, it is difficult to completely remove, and so while there is a good prognosis, recurrences or persistence may be seen. There is no metastatic potential. Patients who succumb to the disease, usually do so because of other tumors within the von Hippel-Lindau complex rather than from this tumor. Surgery is the primary treatment modality, but in some rare instances adjuvant radiation therapy may be used. Epidemiology
This is a very rare tumor, since only about 1 in 35,000 to 40,000 people have VHL, of whom about 10% have endolymphatic sac tumors. Patients usually present in the 4th to 5th decades without an gender predilection. The tumor involves the endolymphatic sac, a portion of the intraosseous inner ear of the posterior petrous bone. References
Further reading
Lester D. R. Thompson; Bruce M. Wenig (2011). Diagnostic Pathology: Head and Neck: Published by Amirsys. Hagerstown, MD: Lippincott Williams & Wilkins. pp. 7:64–67. ISBN 978-1-931884-61-7.