Lactate uptake by tumors feeds their oxidative metabolism [212, 216, 219] and requires the importer MCT1, a marker of mitochondrial activity and stemness in cancer and a target gene of the fusion protein ASPSCR1/TFE3 in alveolar soft part sarcoma (ASPS) [220]. The gene discussed is ASPSCR1; the disease is alveolar soft part sarcoma.