Studies evaluating the protein expression and ubiquatination levels of FANCD2 in breast tumors have also identified an association between BRCA1 (another confirmed high-risk BC gene) and FANCD2 protein expression, and in breast tumors an association between FANCD2 protein expression and tumors size, TNM stage, ER status and Ki-67 index and ultimately, disease-free survival rate. This evidence concerns the gene FANCD2 and breast cancer.