Figure 1: The cancer cell clones in primary stomach tumor (a), meta static liver tumor (b) and metastatic esophagus tumor (c). The main tumor subclones are marked in yellow. The different level of yellow in primary and metastatic tumors means the genetic diversity within the subclonal. The red represents the dominate subclone whereas the other color means the minor subclones. The figure indicates that metastatic tumour may arise from the cells within the primary tumour.