We previously reported a retrospective series of MPT individuals (defined as having two primary tumors before 60 years of age) referred to a UK clinical genetics service without pre-assessment and observed that 20.7% (44/212) were found to have a molecular diagnosis upon routine targeted molecular genetic testing, including BRCA1 and BRCA2 testing, mismatch-repair gene analysis, or other single-gene testing (APC [MIM: 611731], MUTYH [MIM: 604933], PTEN, TP53 [MIM: 191170], and RB1 [MIM: 614041]).31