Objective      To investigate the correlation between molecular subtypes and circulating tumor cells (CTCs) in breast cancer.       Methods      The peripheral blood samples were collected from 116 patients with breast cancer and 20 patients with breast fibroadenoma (5 ml of each patient). The mononuclear cells in the blood samples were enriched by density gradient centrifugation

and then were tested by quantitative real-time PCR (qPCR) to detect cytokeratin (CK) 19 mRNA-positive CTCs. The correlation between molecular subtypes and CTCs in breast cancer was analyzed.       Results      The positive rate of CTC in the breast cancer patients was 31% (36/116)

while no CTC was detected in the patients with breast fibroadenoma. The median of CK-19 mRNA-positive CTC (expressed as MCF-7 cell equivalents/2 μg total RNA) in the 36 CTC-positive patients was 1.65 (1.18

2.87). The proportion of luminal type

HER-2 type and basal-like type in the 116 breast cancer patients were 62.1% (72/116)

17.2% (20/116) and 20.7% (24/116)

respectively. The positive rates of CTC in these molecular subtypes were 27.8% (20/72)

35% (7/20) and 37.5% (9/24)

respectively

and no significant difference was observed (P=0.615). The medians of CK-19 mRNA-positive CTC (expressed as MCF-7 cell equivalents/2 μg total RNA) of the three subtypes were 2.1 (1.18

3.9)

1.37 (1.12

2.12) and 1.53 (1.32

2.64)

respectively

and there was significant difference between the different subtypes (P=0.046).       Conclusion      There was significant difference of CK-19 mRNA-positive CTC level between different molecular subtypes of breast cancer

indicating the relationship between the CTC level and the clinical heterogeneity of molecular subtypes in patients with breast cancer.