S-100B Protein, Serum

S100 proteins are localized in the cytoplasm and nucleus of a wide range of cells and play a role in the regulation of a number of cellular processes including cell cycle progression and differentiation.³ S100 calcium binding protein B, or S-100B, is localized predominantly in astrocytes and Swans cells of the central nervous system. Small amounts of S-100B are also found in peripheral locations including adipocytes, melanocytes and other cells.³

Serum S-100B levels can be increased in various neoplastic and neuropathologic conditions including melanomas, malignant peripheral nerve sheath tumors, schwannomas, paraganglioma stromal cells, histiocytoma and clear cell sarcomas.⁴ In clinical practice, S-100B is mainly used as protein tumor marker for assessment of melanoma patients.^5-11 S-100B serum levels can reflect tumor load, correlate with response to treatment, identify patients who are at increased risk of disease relapse, may predict prognosis and could be used as early biomarkers of tumor recurrence.¹² For patients with high-risk surgically resected melanoma, a high baseline or increasing serum S-100B is an independent prognostic marker of risk for mortality¹³ and normal values predict prolonged survival for stage IV melanoma patients.¹⁴ The measurement of S-100B in the diagnosis, follow-up and therapeutic monitoring of malignant melanoma has been suggested by Swiss,⁶ German^7,15 and European Society for Medical Oncology (ESMO)¹⁶ guidelines.

S-100B has been employed as a screening, monitoring and prediction tool in the management of traumatic brain injury (TBI) patients,^17-25 and it has been included into several guidelines as pre-head CT screening test.^19,26-28 S-100B levels are significantly higher in children with TBI compared with healthy matched controls²⁹ and higher in children with a lower presenting Glasgow Coma Scale scores.³⁰ A high S-100B level at admission was associated with poor outcomes at hospital discharge.³¹ Outcome at 6 months post-injury, assessed using the Glasgow Outcome Score, is associated with S-100B levels at admission^32,33 and at one week following injury.³⁰ Time to peak S-100B levels was associated with neurocognitive outcome.³⁴ Two other studies found that admission levels were associated with poor outcome at 12 months post-injury.^29,35