Isolated primary maxillary sinus esthesioneuroblastoma presenting as idiopathic syndrome of inappropriate antidiuretic hormone

Esthesioneuroblastoma is an uncommon tumour, and isolated primary involvement of the maxillary sinus is exceedingly rare. Esthesioneuroblastoma has infrequently been reported as a source of paraneoplastic ectopic hormone production. We report a case of isolated primary maxillary esthesioneuroblastoma, presenting as idiopathic syndrome of inappropriate antidiuretic hormone (SIADH). A 17-year-old girl presented with symptoms consistent with SIADH and no sino-nasal symptoms. MRI to exclude pituitary tumour revealed an isolated lesion of the right maxillary sinus. Biopsy demonstrated esthesioneuroblastoma. The lesion was removed endoscopically as a single en bloc specimen. Following resection, the sodium level returned to normal. This is only the third report in the literature of a primary maxillary esthesioneuroblastoma presenting as SIADH.