Detection of circulating tumour cells and nodal metastasis by reverse transcriptase-polymerase chain reaction technique

Background In the search for occult metastases in lymph nodes or circulating tumour cells, a reverse transcriptase-polymerase chain reaction (RT-PCR) assay was developed to detect tumour-specific splice variants of the transcript of the CD44 gene. The assay was highly sensitive and could detect ten tumour cell per 10(6) leucocytes. Methods RNA was purified from peripheral blood (n = 24) and regional lymph nodes (n = 14) from patients with colorectal cancer. Complementary DNA was made and amplified using primers specific for the CD44 gene, Southern blotting with exon-specific probes was used to enhance the sensitivity. Results Tumour cells were detected in peripheral blood samples in four patients and lymph nodes in nine, in one of whom conventional histology had not detected tumour cells. Conclusion This technique may be useful in the early diagnosis of primary or metastatic tumours, in assessing prognosis and in detecting residual disease after treatment.