Morphologically intact melanoma cells may be detected in peripheral blood of melanoma patients.

Abstract

The detection of circulating melanoma cells has been the subject of numerous investigations in recent years. We developed a cellular approach to identifying circulating melanoma cells in peripheral blood using immunomagnetic cell sorting. The examination covered 205 blood samples from 155 melanoma patients and 30 samples from healthy persons and nonmelanoma patients. After density gradient centrifugation, the interphase was incubated with the 9.2.27 antibody. Positive cells were labeled with magnetic microbeads and enriched by immunomagnetic cell sorting. Cells were stained using an alkaline phosphatase-anti-alkaline phosphatase assay and examined by light microscopy. In spiking experiments, melanoma cells seeded at a concentration of one melanoma cell per milliliter of whole blood could be detected reliably. Circulating melanoma cells were not found in 30 controls, nor were 9.2.27-positive cells found in 41 patients with primary malignant melanoma. In patients with regional lymph node metastases and disseminated disease, circulating 9.2.27-positive cells could be detected in 3 of 29 patients (10%) and 13 of 85 patients (15%) examined, respectively. We conclude that immunomagnetic cell sorting is a promising method with high sensitivity and specificity. The method is not suitable for early detection of metastases but is a valuable tool for further investigating the biological characteristics of circulating melanoma cells.