WT1 and renal cell carcinoma: However, intracytoplasmic lipid, if detected by Oil Red O, along with immunocytochemistry for CD15, RCC Ma (RCC marker) and CD10 (positive in many RCC) may be helpful in this distinction.[8] Immunostaining for mesothelial markers (calretinin, CK5/6, WT-1 and thrombomodulin) may also assist in the distinction.