A Case of Endolymphatic Sac Tumor

Endolympathic sac tumor is a rare temporal bone neoplasm, and is considered to be a low-grade adenocarcinoma. Despite its slow growth and low incidence of association with distant metastasis, this tumor often shows aggressive local bone destruction. Herein, we report a rare case. A 52-year-old man with Down syndrome presented with a 6-month history of hemifacial palsy. The initial examination revealed left-sided complete facial nerve palsy. Analysis of the auditory brain stem response indicated deafness on the affected side. The patient had no vertigo or nystagmus. Computed tomography revealed a well-defined osteolytic soft tissue lesion in the left petrous bone. The lesion was seen as a high intensity on both T1- and T2-weighted magnetic resonance images, and showed heterogeneous gadolinium enhancement. The labyrinth was destroyed, and the internal acoustic meatus was indistinguishable. Under a tentative diagnosis of cholesterol glanuloma, transmastoid biopsy was performed. The histopathological diagnosis was endolymphatic sac tumor. The patient eventually underwent removal of the tumor via a trans-middle cranial fossa approach following preoperative arterial embolization. His postoperative clinical course was uneventful, and he was discharged 19 days after the surgery. Although the facial nerve palsy or hearing loss did not recover, no evidence of tumor recurrence has been seen over a postoperative follow-up period of 32 months. A bibliographic review of the clinical/histopathological characteristics, diagnosis and treatement of endolymphatic sac tumor is presented.