Ectopic ACTH Secretion Induced by an Olfactory Neuroblastoma: A Case Report.

Background: Olfactory neuroblastoma (ONB) is a rare tumor of the nasal cavity. It may sometimes present with Cushing's syndrome due to adrenocorticotropic hormone (ACTH) secretion, making it challenging to diagnose. Methods: A 65-year-old man with hypokalemia and general weakness presented to the emergency department for Cushing's syndrome. Brain imaging revealed a tumor originating from the ethmoid bone with peritumoral cysts. The first biopsy suggested an ectopic corticotropic pituitary adenoma or a well-differentiated neuroendocrine tumor. However, the second biopsy confirmed an ONB, as suspected by the otolaryngologist. Treatment consisted of neoadjuvant chemotherapy, surgery, and radiotherapy. Results: The patient was cured of Cushing's syndrome and remained in remission at 10 years of follow-up. Conclusion: An unusual mode of discovering ONB is via the diagnosis of Cushing's syndrome caused by ACTH secretion, which may manifest throughout the course of follow-up. Imaging analysis and discussion with pathologists are essential to achieve an accurate diagnosis.