Immunohistochemical staining was performed in seven cases (the seventh case was our case) of all included renal MC patients [2,5,6,8,9,11], in five cases [2,5,9,11] (the fifth case was our case), the cells within the cartilaginous areas are positive for S-100, while CD99 and Vim expressed by the poor-differentiated tumor cells are positive in four [5,6,8] (the fourth case was our case) and six patients [2,5,6,9,11] (the sixth case was our case), respectively. The gene discussed is CD99; the disease is neoplasm.