A Rare Case of Malignant Phyllodes Tumor of the Breast in a Patient With a History of Recurrent Fibroadenomas: A Case Report and Literature Review

The distinction between a fibroepithelial tumor and phyllodes tumor of the breast is clinically significant, as phyllodes tumors and fibroadenomas differ in their biological behavior and thus their management. Malignant phyllodes tumors are extremely aggressive, and most cases with metastasis are unresponsive to chemotherapy and carry a poor prognosis. Due to the rarity of phyllodes tumors and, in particular, malignant phyllodes, the literature evaluating this pathology and its outcomes is sparse; there is currently no evidence-based guideline available for its optimal management. A 29-year-old female underwent an excisional biopsy of right breast fibroadenomas on two separate occasions over the course of five years. Upon a third recurrence, ultrasound noted features suspicious for malignancy, and core biopsy showed fibroadenoma. She underwent excisional biopsy of four masses, where pathology showed fibroepithelial lesion with necrosis in one mass, borderline phyllodes tumor in two masses, and a malignant phyllodes tumor in the fourth mass with positive margins. The patient underwent a right simple mastectomy, was found to have metastasis to the lung, liver, and brain nine months after mastectomy, and died 10 months after mastectomy at the age of 36 years. Given the known tumor heterogeneity and the overall diagnostic uncertainty involved in fibroepithelial masses and phyllodes tumors, it is imperative to maintain heightened suspicion and to utilize additional sampling methods when evaluating fibroepithelial lesions with high-risk features, including hypercellularity, necrosis, or recurrence. Additionally, there is a need for further research and definitive management guidelines for patients with borderline and malignant phyllodes tumors who have undergone mastectomy, as these patients still have a high risk of distant metastasis.