RESUMEN
The aneurysmal bone cyst (ABC) of the lumbar spine is an infrequent entity, of undefined nature and aggressive behavior; there are only a few reports in Mexico, so we present the case of a patient with radicular and lumbar pain that progressed to pelvic limb paresthesia. Lesions in the vertebral body of L1 were located with imaging studies and confirmed with biopsy; treatment with corticosteroids was started and later resection of the lesion was performed together with stabilization of the spine using first a posterior approach and at a second stage an anterior approach. Corticosteroid therapy led to remission of tumor progression, so only vacuolated areas and destruction of the posterior wall were found, leading to instability and radiculopathy. This type of lesions usually appears in long bones and less often in the spine, but it is even rarer in the lumbar spine. The prognosis of ABC is usually good, with the exception of the rare cases of extremely disseminated cysts located in the spine. It is therefore important to consider this before deciding what the best approach is for each patient, as well as the appropriate medico-surgical measures.