REVERSE TRANSCRIPTASE-POLYMERASE CHAIN-REACTION FOR EXPRESSION OF TYROSINASE TO IDENTIFY MALIGNANT-MELANOMA CELLS IN PERIPHERAL-BLOOD

Background: Circulating tumour cells in the peripheral blood may be im portant for haematogenous spread of disease. The detection of these ce lls may therefore be a poor prognostic indicator. Reverse-transcriptas e polymerase chain reaction (RT-PCR) of target tumour-specific protein expression has been used as a sensitive and specific method for the d etection of these tumour cells. Initial reports by our laboratory and others suggested RT-PCR amplification of the enzyme tyrosinase is a us eful method for detection of melanoma cells in peripheral blood [1-3]. Patients and methods: In this report, we have evaluated the applicati on of RT-PCR for tyrosinase mRNA as a detection method for melanoma ce lls in a series of 24 patients with advanced, metastatic malignant mel anoma A single round RT-PCR method is described. Results: The single r ound RT-PCR was as sensitive as previously described nested PCR method s, and had the advantage of reduced contamination risks. Blood samples from three out of the twenty-four patients were positive. Conclusions : The frequency of tumour cell detection in peripheral blood from pati ents with advanced disease was lower than previously reported. It may be only small numbers of circulating tumour cells are present at any o ne time in the peripheral blood of patients with malignant melanoma. I f this is the case increased sampling will improve detection frequency . Alternatively, dissemination of melanoma through peripheral blood ma y be a rare event. In our experience, RT-PCR for tyrosinase mRNA as a staging test for melanoma patients must be interpreted cautiously.