Detection of melanoma micrometastases in the sentinel lymph node and in nonsentinel nodes by tyrosinase polymerase chain reaction

The aim of our study was to investigate the metastatic pathways of melanoma cells in sentinel and other regional lymph nodes. The term "sentinel lymph node" means that the first lymph node of the draining site of a primary tu mor is never bypassed in malignant melanoma, In this case lymph node dissec tion would be necessary only when melanoma cells are detected in the sentin el node. Tyrosinase reverse transcriptase-polymerase chain reaction was app lied to search for metastatic melanoma in the sentinel lymph node and in fu rther lymph nodes of a complete lymph node basin in patients who underwent lymph node dissection. In 24 patients with malignant melanoma the draining site of the tumor was marked by lymphoscintigraphy and by intraoperative in jection of patent blue V in the area around the primary tumor. The lymph no des of the affected basin were excised and prepared for histopathologic, im munohistochemical, and molecular biologic examinations. Regarding the senti nel lymph node, 10 of 24 patients showed morphologic evidence for metastase s, three additional patients showed only tyrosinase transcripts, In 11 of t hese 13 cases we found one or more nonsentinel lymph nodes with morphologic ally detectable melanoma cells and/or tyrosinase mRNA, Interestingly, in se ven of 24 patients a positive tyrosinase reverse transcriptase-polymerase c hain reaction was received in nonsentinel lymph nodes, whereas the sentinel lymph node was negative, not only for all histologic examinations but also by tyrosinase reverse transcriptase-polymerase chain reaction. In five of seven patients of the latter group, gp100 reverse transcriptase-polymerase chain reaction was carried out, showing also gp100 mRNA in nonsentinel lymp h nodes only. Our data indicate that the concept of the sentinel lymph node may miss micrometastases. Whether such micrometastases cause a recurrence or a metastasis of malignant melanoma, or can be destroyed by the immune sy stem, remains to be clarified.