Baseline staging of melanoma with unknown primary site: the value of serum s100 protein and positron emission tomography

Dermatology. 2008;217(4):351-5. doi: 10.1159/000155878. Epub 2008 Sep 18.


Background: Baseline staging is important in all melanoma types, including melanoma with unknown primary site (MUP). Staging includes different examination strategies, each with different accuracy.

Objective: To determine the value of serum S100 protein levels and positron emission tomography (PET) in the baseline staging of MUP.

Methods: Twenty patients with MUP were evaluable for the analysis between 1996 and 2007 with both S100 assessment and PET performed for baseline staging.

Results: Serum S100 was elevated in 7 patients (35%). The PET scan detected the metastases in 6 of 7 patients with elevated serum S100 protein showing a strong correlation (p = 0.005). Patients with metastases had significantly higher serum S100 levels (p = 0.01) than the ones without. Serum S100 protein was shown to be discriminative between patients with and without metastases (receiver-operating characteristic, p = 0.012) with 75% sensitivity and 92% specificity.

Conclusion: Serum S100 protein appears to be a sensitive as well as specific marker to detect metastases. We therefore might recommend serum S100 assessment to be included in the baseline staging of MUP.

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Biomarkers, Tumor / blood*
  • Female
  • Humans
  • Male
  • Melanoma / blood
  • Melanoma / diagnostic imaging*
  • Melanoma / pathology*
  • Melanoma / secondary
  • Middle Aged
  • Neoplasm Staging
  • Positron-Emission Tomography*
  • Radiopharmaceuticals
  • Retrospective Studies
  • S100 Proteins / blood*
  • Sensitivity and Specificity
  • Skin Neoplasms / blood
  • Skin Neoplasms / diagnostic imaging*
  • Skin Neoplasms / pathology*
  • Skin Neoplasms / secondary


  • Biomarkers, Tumor
  • Radiopharmaceuticals
  • S100 Proteins