Margin Status and Local Recurrence in Phyllodes Tumours of the Breast: A Canadian Series

Background. Phyllodes tumours of the breast are rare fibroepithelial neoplasms with a propensity for recurrence. While surgical excision remains the standard of care, the optimal margin width is an area of active investigation. Recent studies have questioned the necessity for wide, local excision. Methods. We conducted a retrospective, cohort study of patients with phyllodes tumours treated at our institution between 2003 and 2021. Demographic, histopathological, and recurrence data were captured; malignant phyllodes were excluded. Cox proportional hazard models were used to identify covariates associated with local recurrence. Results. Of 187 patients with phyllodes tumours, 82.9% (n = 155) were classified as benign while 17.1% (n = 32) were borderline. Initial surgical margins were positive in 26.2% (n = 49), < 2 mm in 50.8% (n = 95), and >= 2 mm in 23% (n = 43) patients. Among patients with positive margins, 61.2% (n = 30) underwent margin revision. At a median follow-up of 2.9 years, the recurrence rate was 3.7%. On univariate analysis, only a positive margin at the time of initial surgery and not margin width was significantly associated with a higher rate of disease recurrence (hazard ratio [HR] 9.52, 95% confidence interval [CI] 1.85-49.2), as was a size greater than 4 cm on preoperative imaging (HR 10.78, 95% CI 0.97-120.1). Revision of an initially positive margin was not significantly associated with decreased local recurrence (p = 1). Conclusions. In this large cohort of benign and borderline phyllodes tumours, positive resection margins and not margin width at the initial surgery were associated with a increased recurrence. Individualization of decisions regarding margin reexcision is important.