RACK1 and cancer: Many factors may account for the inconsistent results across studies, including, heterogeneity due to differences in cancers originating from different anatomic sites (as previously stated), distinct IHC results obtained under different conditions (such as staining on fresh or long-term stored sections or antibodies of varying natures), different percentages of tumor cells on various slides as RACK1 may also be expressed in non-tumor cells, affecting the scoring, and inclusion of a small sample size in the subgroup.