ESR1 and breast cancer: FDG uptake is often lower in lobular BC (vs. ductal BC) [15,16,18,19], in low-intermediate grade (vs. high grade) [12,13,14,15,16,17,18] tumors and in ER-positive tumors, compared to triple negative tumors (ER-/PR-/HER2-) [11,13,15,16,17,20,21,22,23].