Pattern of S100-release in benign and malignant diseases beside malignant melanoma

Background: The usefulness of S100 as a prognostic marker and aid in follow-up care in patients with malignant melanoma as well as in individuals with various neurological pathologies is well known. The aim of this study was to investigate its release and clinical relevance in benign and malignant disorders beyond these indications to elucidate tumor and organ specificity of S100. Methods: S100 levels were studied in serum samples of 1856 untreated patients, among them 59 healthy individuals, 358 patients with benign disorders, and 1439 patients with malignant tumors. Results: Healthy individuals had low S100 levels reaching a median of 0.041 ng/mL and 95th and 100th percentiles of 0.096 ng/mL and 0.144 ng/mL, respectively. The medians of patient groups with benign diseases ranged from 0.030 to 0.057 ng/mL, patients with malignant diseases from 0.020 to 0.059 ng/mL, and thus were comparable to healthy individuals. Only 2% of patients with benign diseases, mainly suffering from infectious, autoimmune, or benign gastrointestinal diseases, and 1% of patients with malignant diseases showed slightly higher values than healthy individuals, in most cases up to 0.5 ng/mL. Conclusions: In contrast to many other oncological biomarkers, S100 is only rarely released in elevated levels from most benign and malignant diseases apart from malignant melanoma and neurological diseases, resulting in superior organ and tumor specificity. As potentially influencing factors, severe infectious diseases have to be considered.