Although some investigators recommended surgical removal of the borders between
pituitary adenoma and the surrounding normal pituitary gland, there is so far little documentation of how intensive dissection of the border zone affects the actual clinical remission rate of
pituitary adenomas. We investigated the precise histological characteristics of the boundary, using surgical specimens from patients who underwent intensive resection of "microsurgical pseudocapsule" of
growth hormone (
GH)-secreting pituitary adenomas. Furthermore, we compared the remission rate of
acromegaly between subjects with (Group 1) and without (Group 2) intensive resection of microsurgical pseudocapsule in order to correlate the histological complete resection and endocrinological remission. Histologically, most
adenomas were in direct contact with normal pituitary gland that formed an increased fibrous component facing the
adenoma, without a true histological pseudocapsule. It was impossible to dissect the
tumor at exactly the
tumor--normal pituitary interface for the whole extent of the
pituitary adenoma during surgery, and complete removal of the
tumor inevitably included a portion of normal tissue (microsurgical pseudocapsule). The biochemical remission rate was significantly higher in Group 1 than in Group 2 (90.0 vs 61.1%), and Group 1 showed no additional postoperative pituitary hypofunction. The present results suggested that intensive resection of the microsurgical pseudocapsule is essential to accomplish histological and endocrinological total resection of the
GH-secreting pituitary adenomas for remission of
acromegaly.