IODODEOXYURIDINE LABELING OF S-PHASE FRACTION IN FINE-NEEDLE ASPIRATES FROM BREAST CARCINOMAS

The suitability of measuring the S-phase fraction in human breast canc er by labelling tumour cells from fine needle aspirates (FNAs) in vitr o with iododeoxyuridine (IdU) was studied in 11 patients. The S-phase fraction was measured both in preoperative FNAs labelled in vitro with IdU, and in FNAs taken from the same tumour when surgically removed a fter intravenous administration of IdU, Frozen sections were also immu nostained for incorporated IdU. The mean S-phase fraction measured in FNAs after in vitro or in vivo labelling and in sections after in vivo labelling was 4.0, 3.6, and 3.1, respectively, Results of in vitro an d in vivo labelling of FNAs with IdU were similar. However, as the S-p hase fraction in breast cancer is generally low, the variation between the different measurements is too large; therefore, the S-phase fract ion is not a suitable indicator of response to treatment.