Asynchronous pituitary adenomas with differing morphology.

Recurrent pituitary tumors can sometimes pose a diagnostic and therapeutic challenge. We report a case of a 43-year-old man who presented twice, 13 years apart, with pituitary adenoma marked by headaches, visual impairment, and no signs of endocrinologic abnormality. At initial presentation computed tomographic scan documented a pituitary mass eroding the sellar floor, with suprasellar and parasellar extension. The patient underwent transsphenoidal surgery and the tumor was classified as a silent corticotroph adenoma, subtype 2. Thirteen years later, clinical symptoms of a destructive pituitary mass reappeared. This time, the adenoma revealed typical ultrastructural features of an oncocytoma; it had a different immunocytochemical profile from the first tumor. Given these striking morphologic differences, we consider the two adenomas to represent asynchronous, de novo formations. We conclude that the recurrence of a resected pituitary tumor may also represent a metachronous development of two distinct pituitary adenomas.