Endolymphatic sac tumor located around semicircular canals

We report a case of endolymphatic sac tumor (ELST). A 48-year-old female had recurrent and slowly progressive hearing loss, accompanied with dizziness like Meniereʹs disease. A tumor was located around the semicircular canals, and was detected on CT and MRI. The patient underwent total removal of the tumor using a transmastoid approach. Histopathological examinations agreed with features of an ELST. The tumor was highly suspected to have originated from the rugose portion of the endolymphatic sac or the endolymphatic duct, based on surgical and imaging studies. Structure of the membranous labyrinth was preserved regardless of the existence of the tumor around semicircular canals with bone destruction. ELSTs seem to have an osteolytic or osteophilic nature, by examining patterns of tumor infiltration.