Since non-NE cells in TKO-Nicd1 mice still had metastatic potential, we queried if non-NE cells in metastatic lesions might possess stem-like features that have facilitated colonization and propagation (45) and found that the cancer stem cell marker CD44 (45–47) was highly expressed in TKO-Nicd1 non-NE lung lesions but not in TKO primary NE cells (Supplemental Figure 6A). The gene discussed is CD44; the disease is cancer.