Interest of PS100 assay when (99m)Tc sestamibi scintigraphy failed to identify lymph node metastases of melanoma

The study evaluated the contribution of serum PS100 assay to the detection of lymph node metastases during the follow-up of patients previously treated for a malignant melanoma, in addition to (99m)Tc sestamibi (MIBI) scintigraphy and investigation for gene MDR1, in order to detect chemoresistance phenomena. The study included 37 patients with a clinically questionable lymph node around basin lymphatic areas of the previously surgically-treated malignant melanoma. The sensitivity and specificity of PS100 assay were 91% and 86.5%, respectively. The sensitivity and specificity of MIBI scintigraphy were 95% and 85%, respectively. Overexpression of gene MDR1 was observed in six cases. In the event of negative scintigraphic findings, the concomitant analysis of PS100 levels and the scintigraphic result enabled the metastatic MDR+ patients to be distinguished from the non-metastatic patients. PS100 assay may therefore be proposed for the follow-up of malignant melanoma.