What is Li-Fraumeni syndrome?

Li-Fraumeni syndrome (LFS) is a rare autosomal dominant inherited syndrome that significantly increases the risk of developing certain cancers, such as breast cancer, brain tumours, leukaemia, and bone carcinomas, among others. The syndrome was first described in 1969 by Dr Frederick Li and Dr Joseph Fraumeni Jr. after observing four families with multiple early-onset cancers in children. In 1990, research identified abnormalities in the TP53 tumour suppressor gene as the main cause of this cancer predisposition.² LFS has also been connected to the CHEK2 tumour suppressor gene in some cases.

Although considered rare—with around 500 families documented in the literature—it is believed that more than 1000 multigenerational families remain unrecognised.¹

LFS does not have specific symptoms, but suspicion may arise when a family shows multiple cases of childhood cancer or a pattern of cancers commonly linked to LFS.

What is the TP53 gene?

As previously mentioned, LFS is strongly associated with mutations in TP53, the gene responsible for producing the p53 tumour suppressor protein. It is one of the most frequently mutated genes in human cancers and has been widely studied in oncology.³ Because of its protective role, p53 is often referred to as “the guardian of the genome.”

What is its role in the body?

TP53 plays several essential roles, particularly in responding to DNA damage and cellular stress. When cells are damaged, they may begin to divide uncontrollably and form tumours. Functional p53 reacts to stress signals by:

• Pausing the cell cycle (cell cycle arrest) to prevent the spread of damaged DNA
• Activating DNA repair pathways
• Triggering senescence when repair is possible, but the cell should stop dividing
• Initiating apoptosis (regulated cell death) when damage is irreversible⁴

Through these mechanisms, p53 helps prevent cancer formation by removing or disabling potentially harmful cells.

How does TP53 get damaged?

Because p53 is crucial for tumour suppression, mutations in TP53 can have serious consequences. When mutated, p53 loses its ability to bind DNA effectively and regulate repair pathways. Some mutations even appear to gain functions that promote tumour growth.⁵ 

Mutations may occur in two ways:

Sporadic (non-inherited) mutations

Commonly triggered by environmental exposures such as:⁶

• Carcinogens (e.g., tobacco smoke, contaminated food)
• UV radiation from sunlight: These exposures can cause DNA damage that leads to TP53 alteration

Inherited (germline) mutations

In LFS, most mutations are germline, meaning they exist in reproductive cells and are passed to offspring.⁷ External factors and genetic modifiers may influence how the disease presents.⁶

How is LFS inherited?

LFS results from germline TP53 mutations. Most affected individuals inherit one functional and one mutated copy from a parent with LFS. Because it is autosomal dominant, a single mutated copy is enough to increase cancer risk.⁹

In some cases, a child can develop LFS without parental inheritance due to a de novo mutation, meaning the mutation arises spontaneously in the sperm or egg cell. This explains the variation in cancer type and age of onset between individuals.⁸

Most LFS-related mutations are missense changes occurring in the DNA-binding domain of TP53.¹⁰ People with LFS also have a higher risk of developing second primary tumours, and certain cancers—such as choroid plexus carcinoma, a rare childhood brain tumour—are strongly associated with germline TP53 mutations.^8,10

Family history and risk

A child of an affected parent has a 50% chance of inheriting the mutation. Individuals assigned female at birth show a higher lifetime cancer risk, with reports indicating nearly a 100% chance of developing cancer before age 40, compared to about 73% in males.⁸

How is inheritance confirmed?

Although there is currently no cure for LFS, diagnosis is valuable because it enables regular monitoring and early cancer detection.

Diagnosis is typically based on genetic testing for pathogenic TP53 variants combined with clinical criteria, as some patients may meet clinical features without an identifiable mutation.

Classic diagnostic criteria include:

• A sarcoma before age 45
• A first-degree relative with cancer before age 45
• A second-degree relative with cancer or sarcoma before age 45

Chompret criteria (newer approach)

Diagnosis is considered if any one of the following is met:¹¹

1. An LFS-associated tumour before age 45 plus a first- or second-degree relative with an associated tumour
2. Multiple LFS-associated tumours before age 46 (excluding multiple breast tumours)
3. Adrenocortical carcinoma or choroid plexus tumour, even without a family history¹¹

Summary

Li-Fraumeni syndrome is uncommon, yet likely under-recognised. Awareness of its autosomal dominant inheritance pattern, reliance on family history, and the importance of TP53 mutation testing plays a key role in identifying individuals at risk.

Early recognition enables ongoing monitoring, which may lead to earlier cancer detection and improved outcomes for affected families.