Twelve FFPE tumor sections consisting of 6 estrogen receptor (ER) and/or progesterone receptor (PgR) positive cases, and 6 triple negative breast cancer (TNBC) cases, were spatially analyzed by microproteomics, to provide an unsupervised and unlabeled in-depth proteomic profiling of BC spatial heterogeneity. The gene discussed is ESR1; the disease is triple-negative breast carcinoma.