Knowledge of the role that LCK plays in solid human tumors is developing, with reports that LCK is expressed in human breast cancer specimens [213]; LCK is overexpressed and activated in lung cancer cell lines [214]; LCK is upregulated in bile duct cancer cells and associates with early tumor recurrence [215]; LCK inhibition in human glioma cells decreases malignant progression [216]. The gene discussed is LCK; the disease is breast cancer.