Background: Li-Fraumeni-Syndrome (LFS) is an autosomal-dominant, inherited tumour predisposition syndrome associated with heterozygous germline mutations in the TP53 gene. Patients with LFS are at a high risk to develop early-onset breast cancer and multiple malignancies, among which sarcomas are the most common. A high incidence of childhood tumours and close to 100% penetrance has been described. Knowledge of the genetic status of the TP53 gene in these patients is critical not only due to the increased risk of malignancies, but also because of the therapeutic implications, since a higher rate of radiation-induced secondary tumours in these patients has been observed.Case report: We report a patient with LFS harbouring heterozygous, pathogenic TP53 germline mutation, who was affected by four synchronous malignancies at the age of 40: a myxofibrosarcoma of the right upper arm, bilateral breast cancer and a periadrenal liposarcoma. Radiological treatments and a surveillance program were adjusted according to recommendations for LFS patients.Conclusion: Management of tumour treatment of patients with LFS is different to the general population because of their risk for secondary cancers in the radiation field. Screening procedures should take a possibly elevated risk for radiation induced cancer into account.