Recently, we examined c-MYC copy number variation (CNV) in two cohorts of invasive breast cancer patients using an ecological diversity index, the Shannon index, and we found that a high Shannon index for c-MYC was a significant poor prognostic factor, which suggests that a diversity index of even a single gene can be a measure of intratumoral heterogeneity and can be used as a prognostic indicator14. This evidence concerns the gene MYC and breast cancer.