More recently, a three-compartment model of metabolism has been proposed in normal mucosa and hand and neck squamous cell carcinoma (HNSCC) by Curry et al. In normal mucosa, a hyperproliferative and mitochondrial-rich basal stem cell layer exists that is positive for markers Ki-67, TOMM20, COX, and MCT1. This evidence concerns the gene MKI67 and head and neck squamous cell carcinoma.