In the majority of tumor types, including colorectal carcinoma [193], clear cell renal cell carcinoma [194], esophageal squamous cell carcinoma [195], gastric cancer [196], urothelial carcinomas of the urinary bladder [197], and squamous cell carcinoma of the head and neck [198], increased ALDH1A1 protein expression was correlated with tumor metastasis and an unfavorable prognosis. This evidence concerns the gene ALDH1A1 and neoplasm.