PTTG1 and nonpapillary renal cell carcinoma: After conducting a series of rigorous analyses, such as PPI analysis, survival analysis, expression analyses in stage, grade, and distant metastasis to genes in the pink module, a total of six hub mRNAs (BUB1B, CCNB2, KIF18B, PLK1, PTTG1, and TOP2A) that could predict distant metastasis and poor prognosis in patients with ccRCC were successfully identified.