Grading system and surgical approaches for endolymphatic sac tumors

Purpose Endolymphatic sac tumors (ELSTs) are rare, low-grade adenocarcinomas arising from the endolymphatic sac. This study aims to present a novel grading system for ELSTs to determine the optimal management strategy. Methods We performed a retrospective analysis of 16 patients with 17 ELSTs. The tumor location and involved adjacent neurovascular structures on CT and MRI were selected to establish the grading system. Results Based on the novel grading system, grade III a tumors were most common (7/17), followed by grade I (4/17), grade II (3/17), and grade III b (3/17) tumors. Eight advanced ELSTs (grade III a and III b) received an infra-temporal fossa approach, while the other 6 early stage ELSTs (grade I and II) underwent either a retrolabyrinthine approach with posterior petrosectomy or a translabyrinthine approach combined with subtotal temporal bone resection. Hearing preservation was achieved in 2 grade I patients. Postoperative facial nerve function was HB II in 1 grade III a patient who underwent anterior facial nerve transposition and was HB III in 4 advanced patients who received facial nerve grafts with the great auricular nerve or facial-hypoglossal nerve anastomosis. The mean follow-up time was 35.1 months. Two grade III patients and 1 grade II patient had tumor recurrence during follow-up, among whom 1 grade III b patient had two cases of recurrence. Conclusion A correct initial diagnosis was established in all patients after meticulous imaging studies. Surgical resection is still the first choice to manage patients with ELSTs. The novel grading system enables surgeons to select tailored surgical approaches. Long-term follow-up is necessary following surgical intervention.