Aim The Singapore nomogram was developed to predict recurrence risk of phyllodes tumours (PTs) of the breast based on histological features of stromal atypia, stromal mitoses, stromal overgrowth and surgical margin status. We aimed to validate the utility of the Singapore nomogram in a Korean PT cohort.

Methods One hundred and twenty-four patients with Korean PT who underwent surgical resection between 1996 and 2015 were included in this study. Pathology reports and slides were reviewed to obtain histopathologic features and acquire Singapore nomogram scores. The probability of concordance between predicted and observed survivals by means of the Singapore nomogram was evaluated using a concordance index (C-index).

Results Of the 124 cases, 57 (46%) were diagnosed as benign, 50 (40.3%) as borderline and 17 (13.7%) as malignant. Recurrences occurred in 25 (20.2%) patients. Univariate analysis showed PTs with higher stromal mitotic counts, marked stromal cellularity, stromal overgrowth, positive surgical margin, marked stromal atypia or a malignant grade presented higher risks of recurrence. Multivariate analysis showed stromal mitoses and surgical margin status independently predicted recurrence-free survival. Patients with high nomogram scores were at greater risk of recurrence (HR=1.05, 95% CI: 1.02 to 1.07, p<0.001) with a C-index of 0.762.

Conclusion The Singapore nomogram provided a useful means of predicting PT outcomes in a Korean PT cohort.