ESR1 and breast cancer: Based on the clustering analysis (Fig. 1a, b), we focused on the following comparisons: (I) TIF vs NIF, (II) BC subtypes, (III) cluster 1 vs cluster 2, (IV) high TILs vs low TILs, (V) ER+ vs ER−, (VI) PgR+ vs PgR−, and (VII) high grade vs low/medium grade.