Objective:To study the expression of cytokeratin (CK) 20 in the peripheral blood of patients with transitional cell carcinoma of the bladder and to evaluate its clinical significance.Methods:CK20 mRNA in 63 patients with TCCB

19 non-cancerous patients and 19 healthy volunteers was detected respectively.GAPDH was used as a general marker for normal blood cells.CK20 and GAPDH were amplified by using RT-PCR.Results:Nineteen healthy volunteers and 19 non-cancerous patients showed no CK20 signals in peripheral blood.Sixteen of 63(25.4%) patients with TCCB showed positive CK20 signals in peripheral blood

including 0/31 of stage T 1

2/16 of stage T 2

7/9 of stage T 3

7/7 of stage T 4.The CK20 expression difference between T 1/T 2 group and T 3-4 groups was significant.Two patients with positive CK20 signals in peripheral blood had distant metastases during a 6-month follow-up period.Conclusion:CK20 is applicable to detect cancer cells in the peripheral blood of transitional cell carcinoma of the bladder and may play an important role in the evaluation of the prognosis and postoperative management of TCCB.