Phyllodes Tumor of the Breast: Stromal Overgrowth and Histological Classification are Useful Prognosis-predictive Factors for Local Recurrence in Patients with a Positive Surgical Margin

BACKGROUND: The local recurrence rate of phyllodes tumors is high and ensuring a sufficient surgical margin is considered important for local control. However, the preoperative diagnosis rate of phyllodes tumors is low and we often encounter cases in which a sufficient surgical margin is not achieved, since in routine medical practice the lesion may not be diagnosed as phyllodes tumor until postoperative biopsy of a mammary mass. Furthermore, there are no established therapeutic guidelines for surgical stump-positive phyllodes tumors. We reviewed the outcomes of excision of phyllodes tumors to investigate factors involved in local recurrence and to determine the indication for re-excision in stump-positive cases. METHODS: The subjects were 45 patients treated for phyllodes tumors at our institution from January 1980 to July 2005. Age, tumor size, surgical method, stromal cellular atypia, mitotic activity, stromal overgrowth, histological classification and surgical stump status were analyzed. RESULTS: Median age was 45 years old (range 28-75) and tumor size was 1-17 cm (median 3.5 cm). Pathologic diagnoses were benign, borderline and malignant in 31, five and nine cases, respectively, and the surgical stump was negative in 27 lesions and positive in 15. Median follow-up was 101 months (range 1-273), with local recurrence in six cases and distant metastasis in one. The local recurrence-free rate was 88, 88 and 84% and the disease-free rate was 85, 85 and 81% after 5, 10 and 15 years, respectively. Overall 10-year survival was 97%. In univariate analysis, a positive surgical margin, stromal overgrowth and histological classification were predictive factors for local recurrence after breast-conservation surgery (P = 0.0034, 0.0003, 0.026). A positive surgical stump was the only independent predictor of local recurrence in multivariate analysis (RR 0.086; 95% CI 0.01-0.743, P = 0.012). Stromal overgrowth was a predictive factor for local recurrence in cases with a positive surgical margin (P = 0.0139). CONCLUSION: Wide excision is the preferred therapy for phyllodes tumor and preoperative diagnosis is important for good local control. Re-excision is recommended in cases with a positive surgical margin and stromal overgrowth and malignancy.