Detection of melanoma cells in sentinel lymph nodes, bone marrow and peripheral blood by a reverse transcription-polymerase chain reaction assay in patients with primary cutaneous melanoma: association with Breslow's tumour thickness

Background Tyrosinase reverse transcription-polymerase chain reaction (RT-P CR) has been shown to be highly sensitive in detecting tumour cells in mela noma patients. Objective To assess whether the detection of minimal residual disease by RT -PCR is improved by concomitant analysis of sentinel lymph nodes (SLNs), bo ne marrow (BM) and peripheral blood (PB) in patients with primary melanoma. Methods Thirty-five SLNs, 41 BM samples and 26 PB specimens from 26 patient s with primary cutaneous melanoma (tumour thickness greater than or equal t o0.75 mm) were examined by nested RT-PCR for tyrosinase and Melan-A. SLNs a nd BM samples were also analysed by histopathology. RT-PCR findings were re lated to tumour thickness of the primary melanoma. Results Overall, melanoma cells were detected by RT-PCR in 13 of 26 patient s (50%). Seven patients had positive RT-PCR results in their SLNs (27%), in cluding all patients (n = 4) with histologically positive SLNs, two patient s had positive findings in their BM exclusively detected by RT-PCR (8%) and six patients in PB (23%). The presence of tumour cells detected by RT-PCR in SLNs was not related to the presence of melanoma cells in BM and/or PB. The incidence of RT-PCR-positive SLNs was significantly associated with gre ater tumour thickness (P = 0.004). Both patients with positive RT-PCR findi ngs in their BM had a large tumour thickness (greater than or equal to 2 mi n). No association between positive RT-PCR findings in PB and greater tumou r thickness was observed. Conclusions RT-PCR-positive SLNs were strongly associated with greater tumo ur thickness, underlining the prognostic significance of SLN positivity. Si milar to certain epithelial malignancies, molecular investigation of the BM might provide complementary prognostic information in the early stages of melanoma. In contrast, no association between positive RT-PCR results in PB and increasing tumour thickness was found, implying that RT-PCR findings i n PB are of doubtful clinical relevance in primary melanoma.