Li-Fraumeni syndrome with occult breast cancer identified in contralateral risk-reducing mastectomy

Abstract

　The patient was a 28-year-old woman who was diagnosed with breast cancer after noticing a mass in her left breast. She was diagnosed with hormone receptor (HR) negative, HER2 positive, invasive ductal carcinoma (IDC) of the breast, cT2N0M0, clinical Stage ⅡA. Genetic testing revealed a pathogenic variant of the TP53 gene, confirming LFS. Following neoadjuvant chemotherapy, she underwent a left skin-sparing mastectomy and a right risk-reducing mastectomy (RRM) based on her preference. The surgical pathology results showed a pathologic complete response in the left breast, while two occult cancers were found in the prophylactic right breast specimen. She completed postoperative anti-HER2 therapy and continues with LFS surveillance. This is the first reported case in Japan in which RRM was performed on a patient with LFS as far as we investigated. Furthermore, this case is significant as it identified two occult cancers in the risk-reduced resected breast, underscoring the importance of RRM. LFS should always be considered when evaluating patients with young-onset breast cancer.