[Demonstration of fetal-type thymidine kinase in cancer of the breast].

Seventy five human breast cancers were examined in order to search for the presence of thymidine kinase of the fetal-type (TK-F). The presence of TK-F was evidenced in all tumors. Its activity varied from one to another tumor, but it was evident that the increased TK activity observed in mammary cancers could exclusively be related to high TK-F activity. Some relations between TK-F activity and the presence of estradiol and progesterone receptors (ER, PR) were obvious. The highest activities were observed in cancers with high level of ER and PR. Thymidylate kinase activity (d-TTP synthesis) varied in parallel with TK-F activity. In a general way, it was higher in ER+ PR+ than in ER+ PR- cancers.