Is increased serum S-100 protein concentration a marker of metastasis in malignant melanoma? A four-year experience report

Between October 1999 and October 2003, S-100 serum protein concentration was measured in 880 samples obtained from 178 consecutive patients with histologically-confirmed malignant melanoma. S-100 concentration was measured with an assay based on three monoclonal antibodies against bovine S-100 protein B-subunit, using an automated chemiluminescence analyzer (Liaison, Diasorin, Saluggia, Italy). This method is much faster (less than 1 h) than the available technology which has been employed in most of previous studies in this field, and allows the surgeon to integrate S-100 concentration levels in his decision-making about patient management and follow-up scheduling. Seventeen out of 178 patients (9.55%) had local or distant metastasis. In 14 of them (82.35%), S-100 levels were higher then 250 ng/L (decision level) when disease progression was detected. Furthermore, the follow-up for five patients showed that a renewed rise of S-100 concentration reflected a new tumor recurrence. Our results confirm that serum S-100 concentration rises with disease progression, and that increased levels are often the first symptoms of recurrence. Furthermore, the study adds to this notion the clinical gain provided by availability of S-100 values before patient evaluation. The management of patients is greatly improved, with benefit to both patient and surgeon.