A 35-year-old woman is found to carry a germline mutation in the TP53 gene. Which syndrome is she at risk for, and what is the characteristic feature of this inherited cancer predisposition?

## Li-Fraumeni Syndrome (LFS) **Key Point:** Li-Fraumeni syndrome is an autosomal dominant cancer predisposition syndrome caused by germline TP53 mutations. It is characterized by early-onset malignancies across multiple organ systems. **High-Yield:** TP53 mutations account for ~70% of LFS cases. Affected individuals have ~90% lifetime cancer risk by age 70, with multiple independent primary cancers being common. ### Spectrum of Malignancies in LFS | Cancer Type | Frequency | Age of Onset | | --- | --- | --- | | Breast cancer | Most common in women | <40 years | | Soft tissue sarcoma | 15–20% | Childhood/young adult | | Osteosarcoma | 5–10% | Childhood | | Brain tumors | 5–10% | Childhood | | Adrenocortical carcinoma | 5–10% | Childhood | | Leukemia | 5% | Childhood | | Gastric, pancreatic, lung cancers | Variable | Adult | **Clinical Pearl:** The "classic" LFS triad is: (1) early-onset breast cancer in women, (2) soft tissue sarcoma, and (3) adrenocortical carcinoma in children. However, any early-onset or multiple primary malignancies in a family should raise suspicion. **Mnemonic:** **TP53 = "The Protector" Gene** — when mutated, it loses its ability to suppress tumors across all tissues, leading to diverse malignancies. ### TP53 Function 1. **DNA damage sensing:** Detects genomic stress 2. **Cell cycle arrest:** Activates p21 to halt G1/S progression 3. **Apoptosis:** Triggers programmed cell death if damage is irreparable 4. **Loss in LFS:** Cells escape checkpoint control → accumulation of mutations → cancer **Warning:** Patients with LFS should avoid unnecessary radiation (including screening mammography before age 40 unless clinically indicated) and chemotherapy when possible, as these can trigger secondary malignancies.