Clinical features, prognostic factors, and treatment outcomes in 611 patients with phyllodes tumors of the breast: The experience of a single institution in Taiwan

Background: Phyllodes tumors are uncommon biphasic breast tumors for which clinical findings remain insufficient to determine the optimal management strategy. The aim of this study was to report our experience of the clinicopathological features, prognostic factors, surgical treatment, and outcomes of patients presenting with phyllodes tumors in two different periods. Materials and Methods: We retrospectively reviewed the clinical and pathological data of 611 patients with histologically proven phyllodes tumors. The patients were separated into two groups: Period A, those who were treated from January 2006 to August 2013, and period B, those who were treated from September 2013 to September 2019. Clinical characteristics, histopathologic parameters, and outcomes were collected from patient records, and parameters were compared between the two periods. Results: The median follow-up was 7 months (range 0.5–84) in treatment period A and 14 months (range 0.5–118) in treatment period B. The median age was 38 years (range 12–75) in treatment period A and 40 years (range 12–79) in treatment period B. Analysis of the two treatment periods revealed an increase in tumor size at the diagnosis from 3.6 cm during period A to 4.5 cm during period B (P = 0.001). Most tumors were found in the upper outer quadrant, with an equal propensity to occur in either breast (34.6% vs. 42.2%). The pathologic diagnoses included 419 benign, 97 borderline, and 40 malignant lesions. Sixty cases (20 in period A and 40 in period B) experienced recurrence after surgery, including 35 benign phyllodes tumors (43% vs. 57%), 16 borderline tumors (38% vs. 63%), and 9 malignant tumors (44% vs. 56%) in either period (P = 0.003). Three cases (0.5%) (1 in period A and 2 in period B) had pulmonary metastases (0.3% vs. 0.7%). Multivariable linear regression analysis revealed that tumor size and a positive or undetermined surgical margin were the independent predictors of recurrence (P = 0.006, 0.020, and 0.004, respectively). Conclusion: Breast-conserving surgery with clear margins is technically feasible and a safe treatment for phyllodes tumors, but this strategy does not effectively further reduce local recurrence. Our findings demonstrated that clinical characteristics, tumor size, surgical margin, and pathologic features are the important predictors for tumor recurrence in patients with phyllodes tumors.