Background: Colorectal cancer (CRC) is the third most common cause of cancer-related death in the US. One out of four patients presenting with conventionally staged node negative disease (AJCC Stage I and II), and over 50% of patients with Stage III disease will develop local recurrence and/ or metastases. Across all stages, approximately 30% of patients will develop distant metastases. Once metastases become clinically evident prognosis is often fatal. Biomarkers capable of predicting progression, risk stratification and therapeutic benefit are needed. CRCSC markers will identify a group of patients at high risk for progression. ALDH1 has been reported as a cancer stem cell marker in pancreatic, breast, prostate, and lung cancer, multiple myeloma and leukemia. By IHC analysis, human ALDH1B1 was found to be expressed at high levels in the small intestine, liver, and pancreas, and at lower levels in the lung and colon. This study aims to investigate ALDH1B1 expression in different types of colorectal carcinoma and correlate this expression with different clinicopathological parameters.
 Materials and Methods: ALDH1B1 immunostaining was studied in 50 specimens of colorectal carcinoma using avidin-biotin peroxidase method. Results: ALDH1B1 was strongly expressed in 12/50 (58%) of cases of colorectal carcinoma, moderately expressed in 31/50 (36%) of cases and weekly expressed in 7/50 (6%) of cases. ALDH1B1 expression in colorectal carcinoma was significantly positively correlated with tumor size (p= 0.021), tumor grade (p= 0.035) where the highest expression levels were associated with moderately or poorly differentiated tumors and positive regional lymph node status (p= 0.038).
Conclusion: The up-regulation of ALDH1B1 with increasing grade of colorectal carcinoma and presence of LN metastases indicates that ALDH1B1 might play a role in carcinogenesis and tumor progression.