Endocrine Abstracts

Background: Most cases of Cushing’s disease originate from the pituitary, rarely the source of excess ACTH is from an ectopic pituitary adenoma.

Case: A 34-year-old woman had a 12-month history of a labile mood, weight gain, easy bruising, irregular menses and hypertension, she appeared cushingoid. Biochemical investigations demonstrated hypercortisolism: 24 h urine-free cortisol 520.7 μg (4–50), ACTH 152 pg/ml (8–42); midnight salivary cortisol 510 ng/dl (<100), 0800 h serum cortisol 28.5 mcg/dl (6.5–26) after a 1 mg overnight dexamethasone suppression test (DST). There was a 70% suppression of cortisol after an overnight high dose (8 mg) DST, and a 50% increase in ACTH during a corticotropin releasing hormone (CRH) test. MRI of the sella revealed an atypical enhancing mass (0.7×0.9×0.5 cm) lying above the pituitary gland, the pituitary gland was normal. Transsphenoidal exploration without inferior petrosal sinus sampling (IPSS) was undertaken. A lesion located wholly in the suprasellar intracranial space, with its inferior aspect lying on but not transecting the diaphragm sella, was removed. No tumour was identified within the sella or pituitary. Pathology revealed a pituitary adenoma, with ACTH immunopositivity. At 6 months follow-up she remains in remission, with preservation of anterior pituitary function.

Discussion: Various locations of ectopic pituitary adenomas have been reported, including the sphenoid sinus, nasopharynx, intracavernous sinus. Ectopic pituitary tumours have been proposed to arise mainly from pituitary rest cells from the embryonic remnants of Rathke’s pouch, from aberrant migration of pituitary cells or from neoplastic transformation of the pharyngeal pituitary. They can be difficult to diagnose because of their small size and unusual locations.

Conclusion: In patients with Cushing’s disease, careful preoperative review of sellar imaging is imperative. These ectopic tumours are not always visible on imaging, and may explain why some patients with Cushing’s disease have residual hypercortisolism after hypophysectomy.