MKI67 and adenocarcinoma: Given the fact that human high grade PIN and adenocarcinoma lesions typically show a range of proliferative fraction (as indicated for example by Ki67 staining) of between approximately 3–40%, MYC levels in these lesions cannot be elevated simply as a reflection of increased proliferation since in most cases where MYC is overexpressed in human PIN and/or adenocarcinoma, many more cells stain positive for MYC (often 60%–80% of cells stain positive) than could be accounted for by simply increased proliferative fraction [31].