ESR1 and breast carcinoma: Previous data exploring the prognostic effect of specific somatic mutations in ER+/HER-2− early-stage breast cancer have shown that PIK3CA and MAP3K1 (mitogen-activated protein kinase 1) mutations co-associate and patients with tumors harboring both mutations have a more favorable clinical course than those with only one gene mutation or without any of these two mutations.27 This may suggest that PIK3CA mutation alone is not prognostic in general breast cancer patient population, nor is it in ILC specifically.