Objective:To study the expression of small breast epithelial mucin(SBEM) in the peripheral blood of  the patients with breast cancer, and explore the correlation between micrometastasis and SBEM.
Methods:Peripheral blood samples were obtained from 92 patients with breast carcinoma, 20 patients with benign breast diseases,10 patients with malignant tumor not originating from breast,and 10 normal healthy volunteers. SBEM-mRNA expression was detected by nested reverse transcription-polymerase chain reaction (Nested-RT PCR).
Results:Among 92 breast carcinoma patients, 43 (46.7%) were Nested-RT-PCR positive for SBEM-mRNA, but it was negative in all the other groups. The expression of  SBEM-mRNA in peripheral  blood did not  correlate  with ER or PR status, menstruation state or primary tumour size. but correlated  with  patient′s age, the state of Her-2,CEA, CA15-3 and axillary lymph node metastasis of breast cancer.
Conclusions:The expression of  SBEM-mRNA in peripheral blood of  breast cancer can be of potential use to monitor the micrometastasis of  breast cancer.