Background: Malignant/borderline phyllodes tumors (PTs) are rare, and little is known about their long-term prognosis. This study sought to evaluate recurrence rates and identify factors associated with local and distant failure.
Methods: From 1957 to 2017, we identified 124 patients with 125 PTs (86 malignant and 39 borderline). Recurrence rates and survival were assessed using the Kaplan-Meier method, and correlated with clinicopathologic factors using the log-rank test.
Results: The median age of the patients was 44 years, and the median tumor size was 5 cm. Breast-conserving surgery was performed for 57% of the patients. At a median follow-up of 7.1 years, 14 patients experienced a locoregional recurrence (LRR), with a 10-year cumulative LRR incidence of 12%. On univariable analysis, age younger than 40 years (p = 0.02) and close/positive margins (p = 0.001) were associated with increased risk of LRR. Seven patients developed distant disease, all occurring in malignant PTs. The 10-year distant recurrence-free survival was 94%. Uniformly poor pathologic features consisting of marked stromal cellularity, stromal overgrowth, infiltrative borders, and 10 or more mitoses per 10 high-power fields (hpf) were identified in 25 PTs (20%), and all distant recurrences occurred in this group. For the patients who did not have uniformly poor features, the 10-year disease-specific survival was 100%, and the overall survival was 94% compared with 66% and 57%, respectively, among those with poor features.
Conclusion: Malignant/borderline PTs without uniformly poor histologic features have an excellent prognosis after surgical resection, with a 10-year disease-specific survival of 100%. The presence of uniformly poor pathologic features predicts a poor prognosis. Efforts should be directed toward new treatment approaches for these tumors.