Immunohistochemical determination of growth fraction in human tumors

The growth fraction in 93 cases of human tumors was estimated by an immunohistochemical staining using Ki-67. The tumors consisted of the following: 14 oral cancers, 14 breast cancers, 9 gastric cancers, 9 uterine cancers, 8 ovarian cancers, 6 colo-rectal cancers, 6 thyroid cancers, 5 esophagus cancers and 22 miscellaneous tumors. Regional labeled cells were predominantly found in the periphery of the tumor nests in squamous cell carcinomas. However, in adenocarcinomas the labeled cells were randomly distributed in tumor cell nests. The Ki-67 labeling index varied greatly from case to case (almost 0 to 50.9% with an average of 17.3%), even within the same organ group. The growth fraction was independent of the histological pattern, although thyroid cancers showed a lower labeling index than other malignant tumors. The labeling indices in benign tumors were lower than those in malignant tumors. The usefulness of this method for the estimation of biological behavior of human tumors is suggested.