S-phase fraction of human tumors and preneoplasia.

Biopsies recovered from human tumors and their preneoplasias (n = 250) were incubated in vitro with 3H-Thymidine, and histoautoradiographic labeling indices (TLIs) were measured. We studied cervical carcinomas and dysplasias of the squamous epithelium of the cervical portio: oral carcinomas and leukoplakias; breast carcinomas and fibrocystic mastopathies; basal cell epitheliomas as well as cerebral tumors of differing degree of malignancy. In each case 2000 to 4000 cells were counted. The relevance of the procedure was examined in methodological investigations. The most important results can be summarized as follows: TLIs represent a relative measure of the size of S-phase fraction of malignant tumors and their behaviour runs parallel with different rate growth. Even for tumors of the same histologic type (Squamous cell carcinoma of the cervix uteri: invasive-ductal breast carcinoma) TLIs are proliferation-kinetic parameters of prognostic significance, in that they characterize the different degrees of malignancy of such tumors. If account is taken of certain conditions, the reliability of the indices is not greatly affected by the intratumoral heterogeneity of cell proliferation. TLIs are more reliable than is histologic description in determining the proliferative potential of dysplasic epithelial changes and various forms of malignancy.