ABCG2 and squamous cell carcinoma: The expression and localization of ABCG2, which has been associated with invasion, metastasis, and resistance to chemotherapy in squamous carcinoma and laryngeal carcinoma [18], and is an unfavorable prognostic factor in HNSCC [17], were evaluated by us to investigate the cell-type-specific localization of p75NTR and p75ICD in CSCs in LSCC.