Endolymphatic sac tumor (aggressive papillary tumor of middle ear and temporal bone): sine qua non radiology-pathology and the University of Texas MD Anderson Cancer Center experience

Abstract

Endolymphatic sac tumor (ELST) is a rare lesion of the skull base for which the origin has recently been ascertained. The endolymphatic sac is derived from neuroectoderm and is located subjacent to the posteromedial surface of the temporal bone. Patients characteristically present with hearing loss, tinnitus, and vertigo; facial nerve paralysis occurs less commonly. An indolent clinical course and long-standing symptom history is typical. Endolymphatic sac tumors are known to occur more frequently in patients with von Hippel-Lindau disease, but this is not a prerequisite for diagnosis because sporadic occurrence is common. Morphologically, all of the ELSTs showed a papillary and glandular architecture. The papillary and glandular structures were lined by a single layer of flattened cuboidal-to-columnar cells that were variably ciliated. Surgery is the treatment of choice for small ELST. Remission may last for years, but local recurrence after surgery, likely secondary to incomplete resection, can occur. Radiotherapy has a 50% cure rate with large or residual tumors. Endolymphatic sac tumor is a rare tumor that can easily be confused with other papillary lesions on histopathologic grounds, with significant treatment implications. Precise preoperative anatomic localization and computed tomography and magnetic resonance imaging feature interpretation play a paramount role in achieving an accurate final diagnosis.

Introduction

Endolymphatic sac tumor (ELST) is a rare lesion of the skull base for which the origin has recently been ascertained. In 1988, Gaffey et al [1] reported a series of 10 cases of an aggressive papillary middle ear tumor characterized by a locally aggressive papillary growth pattern, bone destruction, and frequent endolymphatic sac invasion, thus establishing an entity separate from middle ear adenoma. In 1989, Heffner [2] reported 20 cases of an identical tumor and proposed an endolymphatic sac origin. Before these reports, Hassard and colleagues [3] in 1984 had described intraoperatively a tumor adherent to the endolymphatic sac while performing decompression surgery for presumed Meniere disease. According to the recently published World Health Organization tumor classification, ELST is synonymous with Heffner tumor and aggressive papillary middle ear tumor [4].

The endolymphatic sac is derived from neuroectoderm and is located subjacent to the posteromedial surface of the temporal bone (Fig. 1). The distal part is ensheathed by 2 layers of dura mater, and the intermediate rugose part lies within the vestibular canal. It is from the latter part that ELST is suspected to originate [2], [5]. This anatomic location is important because it explains the propensity of the tumor to involve the petrous portion of the temporal bone as well as cerebellopontine angle structures [6], [7], [8], [9], [10], [11]. There are 4 potential vectors for tumor extension: posteromedially into the cerebellopontine angle, laterally toward the middle ear, superiorly toward the middle cranial fossa, and anteromedially along the petrous ridge toward the cavernous and sphenoid sinuses. Individual examples may grow primarily along one of these vectors or along multiple vectors.

Patients characteristically present with hearing loss, tinnitus, and vertigo; facial nerve paralysis occurs less commonly. Large tumors with growth along the posteromedial vector may cause symptoms secondary to cerebellopontine angle invasion. An indolent clinical course and long-standing symptom history is typical [7], [8], [9], [10], [11]. Endolymphatic sac tumors are known to occur more frequently in patients with von Hippel-Lindau (VHL) disease, but this is not a prerequisite for diagnosis because sporadic occurrence is common. Patients with VHL disease are more likely to have bilateral ELSTs [12], [13], [14], [15], [16].

We present here the MD Anderson Cancer Center (MDACC) experience with ELST including evaluation, diagnosis, and management.