The majority of pituitary adenomas are trophically stable and change relatively little in size
over many years. A comparatively small proportion behave more aggressively and come to
clinical attention through inappropriate hormone secretion or adverse effects on surrounding
structures. True malignant behaviour with metastatic spread is very atypical. Pituitary
adenomas that come to surgery are predominantly monoclonal in origin and roughly half are
aneuploid, indicating either ongoing genetic instability or transition through a period of …