CSPG4 and neoplasm: We can hypothesize that: (i) tumors mainly develop from NG2/CSPG4-negative cells, in spite of the co-existence of positive ones under in vitro cultures, (ii) the latter have lost the capability of expressing NG2/CSPG4 during the malignant transformation, or (iii) the microenvironment triggers tumor cells towards stemness [95] and, therefore, NG2/CSPG4 negativity.