Concurrent ductal carcinoma in-situ and malignant phyllodes with tp53 mutation in an 11-year-old

Phyllodes breast tumours are a rare fibroepithelial lesion that rarely occur in the pediatric population. Reports for benign phyllodes tumours have been limited to case series while only two reports have reported borderline or malignant tumours in children. We report the case of an 11-year-old female presenting with a borderline malignant phyllodes tumor and associated ductal carcinoma in situ (DCIS). We present an interesting case outlining the pathological assessment, surgical management, reconstruction, and subsequent genetic diagnosis of Li-Fraumeni Syndrome. We discuss the importance of multidisciplinary collaboration required and challenges undergoing treatment of rare pediatric breast cancer. To our knowledge, this is the youngest case of a phyllodes tumor within a DCIS field defect in an adolescent female reported to date.