Although these four lymph nodes were pathologically diagnosed to be non-metastatic, we detected the KRAS mutation, which was found in the primary tumor, in DNA isolated from all four lymph nodes with ddPCR, suggesting a presence of a small number of tumor cells or phagocytosed tumor cells that might have primed anti-tumor reactivity (Fig. 2b). The gene discussed is KRAS; the disease is neoplasm.