In conclusion, we report a case of ACTH-dependent Cushing’s syndrome, caused by an ectopic corticotroph adenoma located in the sphenoid sinus, which perfectly mimicked the features of a classical pituitary ACTH adenoma on a comprehensive hormonal evaluation including BIPPS, and the features of a benign naso-sinusal polyp at MRI. The gene discussed is POMC; the disease is Cushing syndrome.