56 Estrogen Receptor Positive Breast cancer tissues coming from patients treated with tamoxifen upon recurrence (41 Good outcome vs 15 Poor outcome) have been microdissected to enrich for breast cancer tumor cells. Enriched tissue has been lysed and proteins digested and analyzed in an LTQ-Orbitrap coupled online with a Dionex nLC system. Thermo output .RAW files were analyzed through MaxQuant (version 1.4.1.2) using the human proteome FASTA (version 2012-09, human canonical proteome) as search library. LFQ parameters in MaxQuant have been enabled (Fast LFQ) and other settings have been kept as default.