In adults, AXL expression is relatively low [40, 41], but aberrant expression of Gas6/AXL has been shown in a number of human malignancies, including breast cancer, chronic lymphocytic leukaemia (CLL), NSCLC, pancreatic cancer, glioblastoma, melanoma, renal cell carcinoma (RCC), prostate cancer, and oesophageal cancer [4, 23, 42–55], and this altered expression is associated with disease progression and shortened overall survival (OS). This evidence concerns the gene AXL and breast cancer.