The liver is often the only site of metastatic disease in patients with colorectal cancer, and such patients are considered for local therapies such as liver resection or tumor ablation. The 5-year survival rate for surgically treated patients is approximately 30% (1). Disease recurrence may be related to intraoperative factors such as the shedding of tumor cells or may be a manifestation of clinically occult disease. Circulating tumor cells (CTCs) in patients with hepatic metastases from colorectal cancer have been identified preoperatively and postoperatively, and intraoperative levels have been shown to correlate with tumor relapse (2, 3). These studies have used the polymerase chain reaction (PCR) detection method of cytokeratin-20 (CK-20)-positive cells to detect CTCs. However, this method is not commercially available.