CD274 and head and neck squamous cell carcinoma: Similarly, Theodoraki et al. isolated exosomes from the plasma of HNSCC patients and found higher exosomal PD-L1 expression in patients locating in UICC stage III/IV or with positive lymph nodes than those patients who were UICC stage I/II or without lymph node metastasis [93], indicating that the expression of PD-L1 in exosome circulation may serve as a biomarker for predicting tumor prognosis.