OBJECTIVE: to report the case of endolymphatic sac tumor (elst). Report: a 46-year-old man presented with continuous tinnitus on his left side, vertigo, and rapidly progressive hearing loss, which evolved to deafness in 15 days. He did not have any prior otologic antecedents, traumatic brain injury, or changes to the ear-nose-throat (ent) exam. He underwent electronystagmography, which revealed left hyporeflexia. Nuclear magnetic resonance imaging (mri) showed an expansive lesion located adjacent to the back face of the left petrous bone, in the topography of the endolymphatic sac, partially obliterating the correspondent cerebellopontine cistern. Computed tomography (ct) showed a hypoattenuating lesion, with discreet peripheral iodinated contrast enhancement and a focal area of cortical destruction of the underlying petrous bone. The lesion was resected using the transmastoid approach, and adenocarcinoma was diagnosed after histopathological analysis. After 7 months of follow up, the patient remains asymptomatic, with no clinical or radiological evidence of recurrence. CONCLUSION: endolymphatic sac tumors are rare neoplasms that occur sporadically or are associated with von hippel-lindau syndrome (vhls). These neoplasms should always be investigated. Clinically, these neoplasms are aggressive, often expanding up to the rear portion of the petrous bone, mastoid, semicircular canals, cerebellopontine angle, and cranial nerves. Patients presenting with elst typically show hearing and vestibular symptoms, and at later stages, neurological alterations, including cranial nerves deficits. Currently, the treatment of choice is complete resection of the lesion. Therefore, it is very important to achieve an accurate and early diagnosis, which is being propitiated by the great technological advancement of imaging.