The majority of cancer mortality is attributed to metastasis, which is the spread of tumor cells to a secondary site. Several studies have demonstrated that the genetic background on which a tumor arises has a major effect on both metastatic efficiency and on predictive gene expression profiles. These observations suggest that there is variability in metastasis frequency between individuals and that some individuals could be more prone to secondary tumor formation and development than others. Thus, genetic background might have important clinical implications in metastasis detection, management and prevention.