Successful treatment of Cushing's disease caused by ectopic intracavernous microadenoma

Adrenocorticotropic hormone (ACTH)-secreting pituitary adenomas are sometimes difficult to visualize, even with high-quality magnetic resonance imaging, due to their small size and variable location. Sampling the cavernous or inferior petrosal sinus is helpful for confirming the central origin of a tumor, but ectopic corticotroph adenomas in the paraseller region also typically exhibit a high central/peripheral plasma ACTH ratio. We experienced an extremely rare case of Cushing's disease caused by an ACTH-secreting microadenoma located entirely inside the left cavernous sinus attached to the medial wall (ectopic pituitary adenoma) that was not visible by preoperative MRI. In this case, the microadenoma was completely removed and an endocrinologic cure was achieved. This case reveals that in addition to meticulous sectioning of the pituitary gland, bilateral periglandular inspection with visualization of the medial wall of the cavernous sinus and of the diaphragm should always be performed to detect ectopic parasellar microadenomas when no adenoma is visible by preoperative MRI.