The packet lists a single gene, TP53 (chromosome 17), with a ClinGen gene-disease validity classification of DEFINITIVE. Inheritance is listed as autosomal dominant. GeneReviews states that most individuals diagnosed with LFS inherited a TP53 pathogenic variant from a parent, and that some have the disorder as the result of a de novo germline pathogenic variant, with the frequency of de novo variants estimated at between 7% and 20%; in one series reporting a 14% de novo rate, about one fifth of the de novo variants were mosaic. GeneReviews notes that a family history may appear negative in some individuals because of unrecognized disease in relatives, small family size, variable expressivity, or late onset of cancer in an affected parent. Penetrance is described as variable and partly dependent on the type of pathogenic variant. For classic LFS, GeneReviews reports an 80% risk of cancer by age 70 years. Low-penetrance TP53 pathogenic variants have also been identified.

GeneReviews describes consensus clinical diagnostic criteria for LFS. LFS is suspected in probands who meet modified Chompret criteria, which combine a tumor in the classic LFS spectrum before age 46 years with a relevant family history, multiple tumors, ACC, choroid plexus tumor, or embryonal anaplastic rhabdomyosarcoma irrespective of family history, or breast cancer before age 31 years. Additional suggestive findings listed include HER2-positive breast cancer before age 40 years, pediatric low-hypodiploid acute lymphoblastic leukemia, and a second primary tumor within a radiation field. A clinical diagnosis is established in a proband meeting all three classic criteria: a sarcoma before age 45 years, a first-degree relative with any cancer before age 45 years, and a first- or second-degree relative with any cancer before age 45 years or a sarcoma at any age. The molecular diagnosis is established by identification of a heterozygous germline pathogenic or likely pathogenic variant in TP53 through molecular genetic testing, which can use single-gene testing or a multigene panel. GeneReviews states that a TP53 variant of uncertain significance neither establishes nor rules out the diagnosis, and that low-level mosaicism for a TP53 pathogenic variant in leukocytes is suggestive of a postzygotic (acquired) variant.

The packet contains no entries in a certified approved-treatments field, so no FDA-approved treatment specific to LFS is certified in this packet. The packet's orphan drug list includes entries for soft tissue sarcoma and soft tissue carcinoma indications, including liposomal vinorelbine, which carries the status DESIGNATED; a designation is not an approval, and these entries are not specific to LFS. GeneReviews management text describes the following. For LFS-related breast cancer, bilateral mastectomy rather than lumpectomy is often used to reduce the risk of a second primary breast cancer and to spare the patient radiation therapy. For other cancers, GeneReviews states that radiation therapy is kept to a minimum where possible because of the risk of secondary malignancies, that conventional cytotoxic chemotherapy may also pose an increased secondary cancer risk and that most experts prioritize treatment efficacy above concerns about late effects; otherwise, standard oncologic management is described. GeneReviews also describes risk-reducing bilateral mastectomy as an option for women with LFS. Surveillance protocols, modified from the Toronto protocol, include periodic comprehensive physical examination, annual whole-body MRI, annual brain MRI, abdominal and pelvic ultrasound, breast imaging, endoscopy and colonoscopy, and dermatologic examination, at age-specific intervals. GeneReviews notes that other published guidelines may differ slightly because definitive efficacy data are lacking. It lists ionizing radiation, unprotected sun exposure, tobacco use, occupational exposures, and excessive alcohol use as exposures whose carcinogenic effects may be cumulative with germline TP53 pathogenic variants. GeneReviews also notes that individuals with LFS may need mental health support because of the burden of intensive surveillance.

The packet does not certify a prognosis or life expectancy. The natural history described in GeneReviews centers on cancer risk across the lifespan: an 80% risk of cancer by age 70 years in classic LFS, with a distribution across childhood, adulthood, and later life. GeneReviews also reports that LFS-related breast cancers are associated with higher rates of ipsilateral breast cancer with breast-conserving surgery, higher rates of contralateral breast cancer, and lower rates of relapse-free survival compared with other individuals with breast cancer. GeneReviews notes that management for low-penetrance variants is evolving.

The packet records ClinicalTrials.gov studies that mention LFS, most of them observational, registry, or screening studies. These include NCT01443468, Clinical and Genetic Studies of Li-Fraumeni Syndrome (National Cancer Institute, recruiting); NCT04367246, the Li-Fraumeni Syndrome/TP53 Biobank (Abramson Cancer Center at Penn Medicine, recruiting); NCT04541654, Li-Fraumeni & TP53 (LiFT UP): Understanding and Progress (Dana-Farber Cancer Institute, recruiting); NCT02950987, whole-body MRI screening in children and adults with LFS and other cancer predisposition syndromes (Dana-Farber Cancer Institute, active, not recruiting); and NCT04982744, a registry of Li Fraumeni and Li Fraumeni-like syndromes (Istituto Ortopedico Rizzoli, recruiting). NCT05126810 (M.D. Anderson Cancer Center) addresses willingness to participate in a genetic counseling trial. Further records can be searched on ClinicalTrials.gov.