The role of Ki-67 in women with a resistant prolactinoma: a retrospective analysis in 199 hospitalized patients over a period of 5 years.

Proliferation-associated antigen Ki-67 is used for the histological evaluation of different tumors. Few studies have been conducted on women with a resistant prolactinoma. To better define the characteristics and to evaluate the differences between patients with different Ki-67 labeling index (LI), a retrospective study was designed to recruit 199 females with a resistant prolactinoma. The patients were divided into two groups, patients with Ki-67 LI≥3% and patients with Ki-67 LI<3%. Tumors in the LI>3% group were also larger (p=0.043), had a higher rate of invasion (p=0.014), and were associated with more frequent polyuria and polydipsia (p=0.008) compared to the LI<3% group. The pre- and post-operative PRL levels in the LI>3% group remained significantly higher compared to patients with LI<3% (p<0.05). The incidences of transient diabetes insipidus and hyponatremia in the LI>3% group were also significantly higher (p=0.037, p=0.041). Additionally, the postoperative PRL normalization rate was lower in patients with LI>3% compared with patients with LI<3% (p=0.028). The recurrence rate in the LI>3% and LI<3% groups were 27.27% and 8.47%, respectively. In conclusion, high Ki-67 LI is predictive sign of a poor prognosis in women with resistant prolactinoma.