ACTH-secreting pituitary adenoma within an ovarian teratoma.

The differential diagnosis of Cushing's syndrome is one of the most difficult tasks in medicine, and it is especially problematic in cases with "occult" ectopic ACTH syndrome. We describe the case of a 26-year-old woman who was found to suffer from ectopic ACTH syndrome due to pituitary microadenoma, localized within a mature ovarian teratoma. Cushing's syndrome caused by ovarian neoplasia is unusual, but when it occurs, it is most often due to excessive cortisol production by the ovary.