Prognostic significance of reverse transcriptase-polymerase chain reaction-negative sentinel nodes in malignant melanoma

Background: Polymerase chain reaction (PCR) is a molecular biology technique that can detect a single metastatic cell in 106 to 107 normal cells. Its use has been proposed as an additional new method for the detection of malignant melanoma nodal metastases in the sentinel lymph node (SLN) to improve the detection rate guaranteed so far by standard histology (hematoxylin and eosin; H&E) and immunohistochemistry (IHC). Methods: Since October 1995, 137 patients with primary cutaneous melanoma (Breslow thickness,.75-4 mm) have undergone surgery for selective lymphadenectomy. To identify the SLNs, every patient had preoperative lymphoscintigraphy and a vital dye perilesional injection, followed by a gamma probe-guided operation. Results: In 134 patients at least one SLN was detected, with a detection rate of 98%. Every SLN was examined by H&E and IHC (S-100 antigen and HMB-45 protein). The messenger RNA codifying for tyrosinase and MART-I (melanoma antigen recognized by T cells) was used as the target sequence for the reverse transcriptase (RT)-PCR. The results showed 11% positive SLNs with IHC and H&E examination and 63% with RT-PCR. No recurrence was noted at follow-up in the group with RT-PCR-negative nodes (absence of false-negative cases). Conclusions: In our experience, RT-PCR SLN negativity is achieving a very favorable prognostic significance. However, RT-PCR positivity is still to be evaluated. Furthermore, results obtained with this method have been shown so far to be independent of Breslow's tumor thickness.