The entire nodule was submitted for pathological assessment, which established the diagnosis of RCC-FMS (Figures 5A–C), immunohistochemically positive for CK, Vim, PAX-8, RCC, CA IX, CD10, SDHB, and FH, partial positive for CK7 and TFE-3, negative for 34βE12, AMACR, and CD117, with a Ki-67 proliferation index of approximately 3% (Figures 5D–I). Here, CA9 is linked to renal cell carcinoma.