Background: S100 proteins are low-molecular-weight calcium-binding proteins and appear to play an important role in various cellular processes such as cell division and differentiation. In histopathology, S100 is widely accepted as the marker of choice for immunohistochemical identification of malignant melanoma. When S100 was detected in the serum of patients with malignant melanoma, it was suggested that serum S100 may be a useful marker for the stage of disease.
Objective: The aim of this study was to examine serum S100 concentrations of patients with different stages of malignant melanoma and to determine the value of serum S100 in the follow-up of melanoma patients during treatment.
Methods: Sera were obtained from 73 melanoma patients in different stages of the disease. The control group consisted of 130 healthy subjects. In 4 patients with metastatic melanoma, serum S100 was measured serially. Serum levels were measured by a commercially available immunoradiometric assay.
Results: While only 1 out of 25 stage I/II patients and 3 of 14 patients with lymph node metastases (stage III, 21.4%) showed detectable serum S100 levels, 27 of 34 patients with disseminated disease (stage IV, 79.4%) had elevated serum S100. Interestingly, rising levels of serum S100 in the serial measurement indicated progression of the disease, and a complete decline reflected 2 patient remissions.
Conclusion: The data support the value of serum S100 as a clinical marker for progression of metastatic melanoma and serological monitoring during systemic therapies.