Phyllodes tumors (PTs) are rare breast tumors characterized by varying biological behavior and heterogeneous clinical findings. As a result, accurately diagnosing PTs preoperatively is challenging, often leading to misdiagnosis. A 49-year-old patient presented with a steadily growing right breast mass that had persisted over a 10-year period. Breast mammography and ultrasonography results indicated the presence of a PT. Following a lumpectomy, the patient was diagnosed with a borderline PT. However, nearly 1 year later, she was readmitted due to the recurrence of a palpable mass at the site. Consequently, 1 year and 8 months after the initial operation, she underwent thoracoscopic lobectomy to address solitary lung metastases. Subsequently, the patient experienced brain metastasis and massive hemorrhage 14 months later. Long-term follow-up was recommended. This case study presents an instance of borderline PT with clinical and imaging features that are crucial for guiding clinical operations and evaluating patient prognosis.Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.