Long-Term Outcomes After Surgical Treatment of Malignant/Borderline Phyllodes Tumors of the Breast

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.

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.

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.

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.