Interest of PS100 assay when Tc-99m 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 treat ed for a malignant melanoma, in addition to Tc-99m sestamibi (MIBI) scintig raphy and investigation for gene MDR1, in order to detect chemoresistance p henomena. The study included 37 patients with a clinically questionable lym ph node around basin lymphatic areas of the previously surgically-treated m alignant melanoma. The sensitivity and specificity of PS100 assay were 91% and 86.5%, respectively. The sensitivity and specificity of MIBI scintigrap hy were 95% and 85%, respectively. Overexpression of gene MDR1 was observed in six cases. In the event of negative scintigraphic findings, the concomi tant analysis of PS100 levels and the scintigraphic result enabled the meta static MDR+ patients to be distinguished from the nonmetastatic patients. P S100 assay may therefore be proposed for the followup of malignant melanoma .