There was no significant correlation between the expression level of ABCG2 and biological factors such as patients' age (p = 0.801), histology type (p = 0.711), histology-grade (p = 0.424), tumour size (p = 0.210), ER (p = 0.136), PR (p = 0.693) and Ki67 (p = 0.906). This evidence concerns the gene ABCG2 and neoplasm.