A case report: invasive ductal carcinoma in mosaic Li-Fraumeni syndrome.

Li-Fraumeni syndrome (LFS) is a rare autosomal dominant condition caused by pathogenic variants in the TP53 tumor suppressor gene and characterized by a high lifetime risk of various cancers with a very early age of onset. We are presenting a 41-year-old woman with right invasive ductal cancer and no family history of cancers, diagnosed with mosaic LFS confirmed with blood and skin punch biopsy samples. She was treated with neoadjuvant chemotherapy, mastectomy and sentinel node biopsy with completion axillary dissection. Adjuvant radiation was not recommended due to increased risk of secondary cancers. She also elected to undergo risk reducing contralateral mastectomy. Further research is warranted to determine the appropriate clinical management and surveillance strategies in patients with mosaic LFS as whether individuals with mosaic LFS have differing cancer risks in comparison to classic germline LFS is unknown.