TP53 and breast cancer: Because patients with BC harboring germline TP53 PVs typically present with very early age of onset, routine TP53 testing has been suggested for women who develop BC before the age of 30 years, independent of family history, and TP53 detection rates within cohorts of patients with early-onset BC have been reported to be between 4% and 8% [8, 13, 14].