NGFR and carcinoma of esophagus: The low-affinity nerve growth factor receptor p75NTR is a putative marker of normal oral and esophageal keratinocyte stem cells [16,17] and has also been suggested as a marker of CSCs in malignant melanoma and esophageal carcinoma [18,19], as well as a determinant of poor prognosis in OSCC [20,21].