ALDH1 immunohistochemical expression and its significance in salivary adenoid cystic carcinoma.

BACKGROUND Adenoid cystic carcinoma (ACC) cells with a high level of ALDH1, a known cancer stem cell (CSC) marker, had higher tumorigenic, invasive, and metastatic abilities. We examined the immunohistochemical expression of ALDH1 in ACC and its correlation with survival. METHODS Archival paraffin blocks of ACC were analyzed. A tissue microarray was constructed and immunohistochemical expression of ALDH1 was analyzed using anti-ALDH1 monoclonal antibody. Correlations between ALDH1 expression and clinical and histological parameters were assessed by chi-square tests. Survival was assessed by the Kaplan-Meier method and log-rank test. RESULTS Most of the tumors (63%) showed stromal staining only, 11% of the tumors showed both epithelial and stromal expression, and 26% of the tumors did not show either epithelial or stromal staining. Statistical analyses did not show any correlation between the pattern of ALDH1 expression and tumor histology, tumor size, or perineural invasion. There were no significant differences in survival among the 3 patterns of ALDH1 expression. CONCLUSION Other factors, besides CSCs, may play important roles in tumorigenesis, cell differentiation, and tumor progression in these tumors.