Ki-67 Labelling Index and Bax Expression According to the Capsular Invasion in the Follicular Neoplasms of the Thyroid

Kim, Hee Kyung; Lee, Dong Wha; Jin, So Young; Kim, Dong Won

Abstract

BACKGROUND
There have been a few studies concerning the differential diagnosis between follicular adenomas and minimally invasive follicular carcinomas, but it is difficult to exclude the possibility of minute capsular and/or vascular invasion throughout the capsular areas as a whole.
METHODS
We examined the diagnostic usefulness of Ki-67 labelling index and bax expression for the differential diagnosis of follicular adenomas and minimally invasive follicular carcinomas.
RESULTS
The result of immunohistochemical staining with Ki-67 and bax antibodies were analyzed in 58 cases of follicular neoplasms from 1996 to 1999. Of 58 cases, 35 were follicular adenomas and 23 were minimally invasive follicular carcinomas. The Ki-67 labelling index was significantly higher in minimally invasive follicular carcinoma of the thyroid (Ki-67 labelling index, 1.62+/-0.35%) than follicular adenoma (0.46+/-0.21%) (P<0.05). Of the follicular adenomas, Ki-67 labelling index of the tumor with 5 cm or more in diameter was 0.38+/-0.13%, while that of the tumor with less than 5 cm was 0.51+/-0.24%. Of the minimally invasive follicular carcinoma, Ki-67 labelling index of the tumor with 5 cm more was 1.30+/-0.07%, while that of the tumor with less than 5 cm was 1.65+/-0.37%. Diffuse bax expression was seen in 27 of 35 cases of follicular adenomas and 2 of 23 cases of minimally invasive follicular carcinoma (P<0.05).
CONCLUSIONS
Our findings suggest Ki-67 labelling index and the degree of bax expression are useful markers for the differential diagnosis between the follicular adenoma and the minimally invasive follicular carcinoma of the thyroid.