Abstract: Objective To explore the clinical value of screening possible serum tumor markers in patients with poorly differentiated nasopharyngeal squamous cell carcinoma. Methods Surface-enhanced laser desorption ionization time-of-flight mass spectrometry （SELDI-TOF-MS）and a CM-10 protein chip were used to determine the serum proteomic patterns of 61 patients with poorly differentiated nasopharyngeal squamous cell carcinoma before radiotherapy and 72 healthy subjects. Proteomic spectra of serum samples collected from 40 patients and 40 healthy controls were used as training sets.The validity of the classification trees were then challenged with blind test sets， which included another 21 patients with poorly differentiated nasopharyngeal squamous cell carcinoma and 32 healthy controls. Biomarker Wizard 3.01 and Biomarker Pattern 5.01 software were used together to analyze the data and develop diagnostic models. Results The accuracy，sensitivity and specificity tested by blinded detection were 86.8%，81.0% and 90.6%，respectively.The accuracy of 3 protein peaks（M4890，M5710 and M7780）was 73.7% for predicting stage I and II，and 81.0% for predicting stage III and IV of poorly differentiated nasopharyngeal squamous cell carcinoma. Conclusion SELDI-TOF-MS combined with bioin-formatics tools provides a new approach for qualitative diagnosis of poorly differentiated nasopharyngeal squamous cell carcinoma.

Key words: Nasopharyngeal neoplasms, Poorly differentiated nasopharyngeal squamous cell carcinoma, Surface-enhanced laser desorption ionization time-of-flight mass spectrometry, Biomarker