Cancer is a heterogeneous genetic disease, and excisional biopsies provide only a snapshot in time of some of the rapid, dynamic genetic changes occurring in tumors. In addition, excisional biopsies are invasive, can’t be used repeatedly, and are ineffective in understanding the dynamics of tumor progression and metastasis.[5] However, liquid biopsy, or blood-sample tests, under development by Epic Sciences can generate actionable information for oncologists by analyzing circulating tumor cells (CTCs)[6] and fragments of tumor-cell DNA that are continuously shed by tumors into the bloodstream.[7] Highly sensitive analysis of individual CTCs have demonstrated a high level of heterogeneity seen at the single cell level for both protein expression and protein localization and the CTCs reflected both the primary biopsy and the changes seen in the metastatic sites. By detecting and quantifying genomic alterations in CTCs and cell-free DNA in blood, liquid biopsy can provide real-time information on the stage of tumor progression, treatment effectiveness, and cancer metastasis risk.[8] This technological development could make it possible to diagnose and manage cancer from repeated blood tests rather than from a traditional biopsy.[6][8][9][10]