Proliferation activity in pituitary adenomas: measurement by monoclonal antibody Ki-67

The monoclonal antibody (MAb) Ki-67 detects a nuclear antigen expressed by proliferating cells during the entire cell cycle. In contrast to conventional histological techniques, the use of MAb Ki-67 on frozen sections or cytological smear preparations allows direct determination of the growth rate of tumors routinely. Sixty-two pituitary adenomas were investigated by use of the MAb Ki-67 in a two-step avidin-biotin-peroxidase complex technique. The proliferation activity ranged from 0.1 to 2.8%. There was no significant difference between the proliferation and hormonal state of the adenomas. Adenomas for which there was histological evidence of dural infiltration, however, showed a statistically significant higher proliferation activity (P less than 0.05) compared to noninvasive adenomas.