Background: Biomarkers in breast neoplasms provide invaluable information regarding prognosis and help determining the optimal treatment. We have examined the possible correlation between cancer stem cell (CSC)-like markers (CD133, paired box gene 2 protein (PAX2), epithelial specific antigen (ESA)), and a new membrane estrogen receptor (G-protein coupled receptor 30 (GPR30)) in invasive ductal breast carcinomas with known clinicopathological parameters, tumor recurrence, and expression of some known biomarkers.

Methods: In 74 invasive ductal breast carcinomas, we investigated the protein expression of these molecular markers by immunohistochemistry, and their associations with known clinicopathological parameters, tumor recurrence, and expression of some known biomarkers. We studied the interrelationship between the expressions of these proteins.

Results: CD133, a putative CSC marker, was positively related to tumor size, tumor stage, and lymph node metastasis. PAX2 was negatively correlated with tumor recurrence. ESA, one of the breast CSC markers, was an indicator of tumor recurrence. GPR30 was associated with hormone receptors. Despite the correlation between GPR30 and the nuclear estrogen receptor, the expression was dependent. Positive staining of GPR30 in tumors displayed a significant association with high C-erbB2 expression and a tendency for tumor recurrence. A positive relationship between GPR30 and CD133 existed.

Conclusion: Detecting the expression of CD133, PAX2, ESA, and GPR30 in invasive ductal breast carcinomas may be of help in more accurately predicting the aggressive properties of breast cancer and determining the optimal treatment.