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(5) 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.