[The clinical significance of detecting small numbers of carcinoma]

The clinical significance of detecting small numbers of carcinoma cells has been emphasized. The techniques for detecting micrometastasis in the bone marrow, lymph node, and peripheral blood have progressed remarkably in recent years with the advance of molecular biology. We use molecular biological techniques, such as reverse transcribed-polymerase chain reaction (RT-PCR) targeting the carcinoembryonic antigen (CEA) gene, and magnetic-activated cell separation system (Miltenyi Biotec Inc., CA) plus modified MASA targeting for K-ras mutation in practical clinical diagnosis and treatment. We herein, we describe how to obtain samples, such as bone marrow, lymph node, and peripheral blood, and how to prepare these samples. We then discuss the pros and cons of tumor specificity and detectability in several methodologies. Thereafter, we describe our strategies with regard to RT-PCR for CEA mRNA and MACS plus MASA method for K-ras mutations. At present, however, we have no consensus for anyone method, and therefore, stress the need to establish an appropriate methodology through a cooperative study.