Specifically, we found that CD44+ breast CSCs are enriched in invasive tumor cell populations 4 and in circulating tumor cell (CTC) clusters that drive polyclonal lung metastases of triple negative breast cancer (TNBC), which lacks expression of estrogen receptor, progesterone receptor, and human epidermal growth factor receptor (HER2) 10. This evidence concerns the gene ERBB2 and neoplasm.