Ki-67 immunostaining of endometrial biopsies with special reference to hormone replacement therapy

The purpose of this investigation was to evaluate the Ki-67 immunostaining method on formalin-fixed, paraffin-embedded endometrium and to use the method on endometrial biopsies from 30 postmenopausal women treated with 2 mg estradiol and different doses of natural micronized progesterone (50, 100 or 200 mg).

Two technicians prepared the immunostaining of slides from each of 12 endometrial specimens and 3 different observers estimated the Ki-67 immunostaining. One observer estimated all the slides 3 times on different occasions. The percentage of immunopositive nuclei in glandular epithelium was evaluated.

The dominating component of variation for this method was between observers, with a median standard deviation of 20%. A total median variation including all components rendered a standard deviation of 23%. No significant effects of different technicians, preparations, or from the same observer on different occasions were found. In the major part of the biopsies from women on hormone replacement therapy (HRT), only 0-10% of the glandular epithelium was Ki-67 stained.

Ki-67 immunostaining is an adequate technique to use when evaluating the effects of HRT on the endometrium. The main source of variation is between observers and not the technique of preparing the slides.