NR2F1 and head and neck squamous cell carcinoma: Many studies have identified NR2F1 as a marker of tumor cell dormancy in breast cancer, HNSCC, prostate cancer, etc. In breast cancer, Borgen et al. [34, 35] analyzed the NR2F1 expression in DTCs by double immunofluorescence (DIF) staining of extra cytospins prepared from 114 BM samples from 86 selected DTC-positive breast cancer patients, and found NR2F1 as a marker of dormancy in breast cancer.