ESR1 and triple-negative breast carcinoma: IC classification stratifies ER+ tumors into ER+ typical risk (IC3, IC4ER+, IC7, and IC8) and ER+ high risk of relapse (IC1, IC2, IC6, and IC9) categories and stratifies triple-negative breast cancer (TNBC) into the genomically stable and unstable subtypes IC4ER− and IC10, respectively (58, 59).