Detection of circulating malignant cells by RT-PCR in long-term clinicallydisease-free I stage melanoma patients

Recently, reverse transcriptase-polymerase chain reaction (RT-PCR) for the detection of circulating tumor cells has been suggested as a potential tech nique for staging cancer. In this report, 43 melanoma patients (including 4 in situ melanoma patients) were tested for tyrosinase mRNA in blood by RT- PCR. All patients had melanoma thinner than 1.5 mm (stage I). Circulating m elanoma cells were defected in 8 (18.6%) out of 43 MM patients tested: 5 (1 6.1%) of 31 patients with melanoma thinner than 0.76 mm and 3 (42.8%) out o f 7 patients with melanoma thicker than 0.76 mm. Moreover; in the tyrosinas e-negative group we found only 4/31 patients (13%) with histologic signs of regression, but in the tyrosinase-positive group, 3 out of 8 patients (37. 5%) showed, at histologic examination, signs of regression. At the time of this analysis all the patients enrolled (tyrosinase-negative and tyrosinase -positive ones) were free of disease,probably due to the short median time of follow-up after the inclusion in the study. I;he presence of regression is an important cause of melanoma understaging and the tyrosinase test coul d represent an effective tool in order to achieve a realistic staging in th is subgroup of melanoma patients. Probably, maximum sensitivity of the diag nostic RT-PCR approach to monitor MM patients with either localized or adva nced disease could be achieved by using additional markers expressed with h igh frequencies in melanoma. We propose that one such marker could be the s ign of regression.