ESR1 and breast carcinoma: Prognostication is routinely performed using clinico-pathologic information; namely the Nottingham Prognostic Index (NPI),23 which comprises tumor size, grade and lymph node status, and an IHC panel to evaluate ER, PR and HER2 (with or without Ki67, a marker of proliferation).24 Ostensibly, the molecular signature market for breast cancer is a busy space (reviewed in ref. 25), however the utility in ILC of some of the existing commercial tests remains to be seen, and uptake is by no means global.