In the study presented here, we assessed the impact of SNPs in the TP53, MDM2, and the MDMX gene on the age-at-diagnosis and event-free survival in a prospective cohort of German breast cancer patients (n = 815) and correlated these data with (i) the TP53-mutational status, (ii) the hormone receptor and HER2 status as surrogate markers for the intrinsic subtypes as well as (iii) clinic-pathological data. The gene discussed is MDM4; the disease is breast carcinoma.