ESR1 and invasive ductal breast carcinoma: To solve the contradiction for which low GART mRNA expression increases the RFS of women carrying ERα-positive tumors but GART mRNA levels are lower in ERα-positive than ERα-negative tumors, we decided to stratify the Metabrick data according to the histological type of the tumor by comparing the invasive ductal carcinoma (IDC - the most frequent one) with all the other types of tumors.