The detection of tyrosinase mRNA in the peripheral blood of stage I melanoma patients is not of clinical relevance in predicting metastasis risk and survival

The presence of tyrosinase mRNA in the peripheral blood cells of melanoma p atients has been recently studied as a possible marker of haematogenous dis semination, However, considerable variations in the rates of detection have been noted. We determined the presence of tyrosinase mRNA positive circula ting cells using reverse transcriptase-polymerase chain reaction (RT-PCR) i n 35 patients with stage I melanoma, two patients with stage II melanoma an d two patients with stage III melanoma. Among the patients with stage I, 13 were tested before and after surgery (< 1 h). Twenty healthy subjects serv ed as negative controls. Out of the melanoma patients, the tyrosinase gene was expressed in three of the 52 samples tested. Tyrosinase mRNA was presen t in the circulating cells of only one patient with stage I melanoma after intra-congenital naevi resection. However, two other stage I patients devel oped rapidly lethal metastasis within the following 6 months, despite the l ack of detectable tyrosinase mRNA. None of stage II patients were positive for the tyrosinase transcripts, while both patients with stage III melanoma showed enzyme expression. Our results confirm those of previous studies, s howing that a small proportion of stage I melanoma patients have tyrosinase -positive circulating cells. Moreover, the lack of tyrosinase mRNA detectio n in the blood does not necessarily exclude metastatic progression. Therefo re, this study indicates that the detection of tyrosinase mRNA-positive cir culating cells by RT-PCR is not a predictive biomarker of a metastasis risk in patients with stage I melanoma. (C) 2000 Lippincott Williams & Wilkins.