ESR1 and breast cancer: We first examined how tumor necrosis was related to molecular markers and subtypes (PAM50) of breast cancer using the TCGA data and found the presence of morphologic tumor necrosis to be associated with molecular features related to more aggressive tumor phenotypes, like estrogen receptor (ER [alpha]) and progesterone receptor (PR) negativity and the Basal-like molecular subtype (all P < 0.001, Table 1, and Fig. 1).