Clinical significance of Ki-67 labeling index in pituitary macroadenoma

Abstract

The aim of our study was to investigate the correlation of the proliferative activity of pituitary neoplasms with clinical characteristics and recurrences. Tumor specimens were obtained from 44 consecutive patients with pituitary macroadenomas who underwent surgery between July 1998 and August 2003. Specimens were immediately fixed in 10% buffered formalin and then embedded in paraffin. The Ki-67 antigen was assessed by immumohistochemical analysis using the monoclonal antibody. We investigated the correlation of the Ki-67 labeling index with the following clinical and radiological characteristics: sex, age, presence or absence visual field defect, tumor classification, maximal tumor diameter, Hardy's classification, type of tumor, invasiveness, and recurrence. Our study suggests that the clinical characteristics such as visual field defect and recurrence are correlated with the high Ki-67 labeling index. No statistical differences were observed in the Ki-67 labeling index in relation to the following characteristics: sex, age, tumor classification, maximal tumor diameter, Hardy's classification, type of tumor, and invasiveness into the sphenoid sinus or cavernous sinus.

Fig. 1

Coronal T1-weighted magnetic resonance (MR) images for radiological invasion of pituitary macroadenoma. Gadolinum-enhanced coronal image (A) shows a homogeneously enhanced intrasellar mass with invasion into the cavernous sinus. Gadolinum-enhanced coronal image (B) shows a homogeneously enhanced intrasellar mass without invasion. In adenomas with invasion, the Ki-67 labeling index was higher than those without invasion.

Fig. 2

Immunostaining for Ki-67 in pituitary macroadenoma. Only the dark brown stained nuclei were considered as immunopositive. (A) The Ki-67 labeling index in recurrent pituitary macroadenoma (3.5%) (original magnification, ×400). (B) The Ki-67 labeling index in non-recurrent pituitary macroadenoma (1%) (original magnification, ×400). The Ki-67 labeling index was higher in recurrent cases than in those without recurrence.