Pediatric Malignant Phyllodes Tumors of the Breast: Characteristics and Outcomes Based on the Surveillance Epidemiology and End Results Database

Background: Malignant phyllodes tumors of the breast are uncommon in women and rare in children. This study aimed to assess the differences in survival among five specific pathologic groups of breast malignancies and the differences between pediatric and adult breast phyllodes malignancy. Materials and methods: Using the Surveillance, Epidemiology, and End Results database, we collected data on 270 pediatric (aged <= 21 y) female breast malignant tumor patients and 2773 female malignant phyllodes tumor patients between 1976 and 2015. We evaluated survival differences among younger patients with breast malignancy and compared the pediatric and adult groups based on characteristics, treatment patterns, and survival months. Finally, we identified the risk and protective factors for breast phyllodes cases using a multivariable Cox analysis. Results: We collected and analyzed 270 malignant breast cancer patients aged <= 21 y and 2773 malignant phyllodes tumor patients. Pediatric patients with malignant phyllodes tumors (22.2%, n = 60) exhibited better overall survival (OS; log-rank, P = 0.012) and cancer-specific survival (CSS; log-rank, P = 0.005) among the younger patients with malignant breast tumors. Furthermore, pediatric patients with malignant phyllodes tumors showed better OS (log-rank, P = 0.004), and similar CSS (log-rank, P = 0.105), compared with older patients. After adjustments for potential confounding factors, age >21 y, Black race, tumor size of >100 mm, high grade, wider invasion, positive nodal status, larger scope surgery, and no surgery were found to be associated with worse OS. All these factors, except for race, were found to be independent risk factors for CSS. Conclusions: The prognosis of malignant phyllodes tumors in children is better than that of adults. Appropriate surgical scope and risk of overtreatment should be considered when treating pediatric malignant phyllodes tumor patients. (C) 2020 Elsevier Inc. All rights reserved.