HIF1A and metastatic malignant neoplasm in the lymph nodes: Innovative extraction and identification of circulating exosomal miR-21 from the serum of patients with oral squamous cell carcinoma and its close affinity with T stage, lymph node metastasis, and HIF-1α expression further supported its prognostic value, as well as the therapeutic value of inhibiting exosomes in the niche [63].