TP53 and Li-Fraumeni syndrome: Classic Li-Fraumeni syndrome diagnostic criteria, based on a study by Li, Fraumeni, and colleagues involving 24 Li-Fraumeni syndrome kindreds, are the following33,34: (1) a member of a kindred with a known TP53 mutation; (2) a combination of an individual diagnosed at 45 years of age or younger with a sarcoma and a first-degree relative diagnosed with cancer at 45 years of age or younger, and (3) an additional first- or second-degree relative in the same lineage with cancer diagnosed at younger than 45 years of age or a sarcoma diagnosed at any age.