As the sole exception worth mentioning, CAIX, known to be inherently expressed in ccRCCs [192,193,194,195,196,197], has shown some predictive value, as lower expression rates are associated with unfavorable outcomes, whereas high density CAIX expression, i.e., in >85% of tumor cells, may be indicative of therapeutic response to combined therapy (interleukin-2 + mTOR inhibitors), but these results still lack validation studies and remain debatable [6]. This evidence concerns the gene CA9 and neoplasm.