PAX8 and renal cell carcinoma: Pathological examination revealed morphological and immunohistochemical findings in line with metastatic renal cell carcinoma, including positive staining for RCC, PAX-8, vimentin and CD10, partial positive for AE1/AE3, and negative staining for Ck7, Syn, α-inhibin, CgA, Melan-A and GATA3, the index of Ki-67 is 20% (Fig. 4).