New Germline TP53 Variant Detected After Radiotherapy-Induced Angiosarcoma of the Chest Wall in a Previously Treated Breast Cancer Patient: A Case Report and Review of Li-Fraumeni Syndrome and Radiotherapy-Induced Sarcoma

Li-Fraumeni syndrome (LFS) is one of the most common hereditary cancer predisposition syndromes in Brazil. The high frequency of the syndrome is due to a founding variant (R337H) in the country. LFS is characterized by a wide variety of malignant phenotypes. Despite the great epidemiological importance of the R337H variant, the frequency of other types of pathogenic variants is like other populations, with the majority of these being missense variants. There is strong evidence that radiotherapy is associated with secondary sarcomas, including angiosarcomas, and this finding is especially true for LFS patients. Angiosarcoma is not described as overrepresented in individuals with LFS, except in patients submitted to radiotherapy. Germline testing in all breast cancer patients under 65 will reveal many germline mutations in TP53 without a family history of cancers associated with the syndrome. We present a case of a previously undescribed pathogenic variant in TP53 (c788del, pAns263llefs⁣^∗82) in a patient with no family history of cancer, with a previous diagnosis of breast carcinoma treated with radiotherapy, who developed angiosarcoma after a few years leading to germline testing. The presence of angiosarcoma in a radiotherapy bed should raise suspicion for LFS. The recent recommendation of testing breast cancer patients under the age of 65, even without any family history, can be a source of discoveries of new mutations and assist in therapeutic decisions.