Low-grade adenocarcinoma of endolymphatic sac origin

CAIX and pax-8 Commonly Immunoreactive in Endolymphatic Sac Tumors: A Clinicopathologic Study of 26 Cases with Differential Considerations for Metastatic Renal Cell Carcinoma in von Hippel-Lindau Patients

Endolymphatic sac tumors (ELSTs) are rare, slowly growing temporal bone neoplasms which show a high association with von Hippel-Lindau (VHL) syndrome. The immunohistochemistry evaluation of these papillary-cystic neoplasms frequently raises the differential diagnosis with renal cell carcinoma, among other metastatic neoplasms, whether in VHL patients or not. A cohort of 26 patients with ELSTs were evaluated for histologic features, immunohistochemistry findings, and association with VHL. Standard immunohistochemistry evaluation was performed. Sixteen females and 10 males ranging in age from 10 to 69 years (mean 44; VHL mean: 32) at initial presentation, comprised the cohort of patients. Most (86%) experienced hearing changes or inner ear symptoms (vertigo, dizziness), with an average duration of symptoms for 39 months (range 2-240 months). The tumors were an average of 2.9 cm (range 0.4-8 cm), with 14 left, 11 right sided and one bilateral tumor. Nine patients had documented VHL, with 3 patients having a concurrent or subsequent clear cell renal cell carcinoma. Patients were followed an average of 6.2 years (available in 24 patients): 19 alive without disease, 7.5 years; 2 dead without disease, 1.2 years; and 3 alive with disease, 3.1 years. The neoplastic cells show the following immunohistochemistry findings: AE1/AE3, EMA, CK7, CAIX, GLUT1, VEGF: 100% of cases tested were positive; pax-8: 85% of cases positive; CD10 and RCC: 0% of cases reactive. Based on this cohort of 26 patients with ELST, 9 of whom had VHL, the strong pax-8 and CAIX should be used in conjunction with negative CD10 and RCC to help exclude a metastatic renal cell carcinoma. As CAIX is an enzyme overexpressed in hypoxia and hypoxia inducible factor is what VHL protein regulates, this is an expected, although previously unreported finding. Whether part of VHL or not, VHL mutations may be a somatic rather than germline finding in the tumors, a possible further explanation for the CAIX reaction.

Current Treatment of Endolymphatic Sac Tumor of the Temporal Bone

An endolymphatic sac tumor (ELST) is a rare, indolent but locally aggressive tumor arising in the posterior petrous ridge. Patients present with sensorineural hearing loss and tinnitus. As the tumor progresses, patients may experience vertigo, ataxia, facial nerve paresis, pain and otorrhea. Most patients present in their 4th or 5th decade with a wide age range. Patients with von Hippel-Lindau disease have an increased likelihood of developing ELST. Histologically, ELST is a low-grade adenocarcinoma. As it progresses, it destroys bone and extends into adjacent tissues. The likelihood of regional or distant metastases is remote. The optimal treatment is resection with negative margins. Patients with positive margins, gross residual disease, or unresectable tumor are treated with radiotherapy or radiosurgery. Late recurrences are common, so long follow-up is necessary to assess efficacy. The likelihood of cure depends on tumor extent and is probably in the range of 50-75%.