P53 expression in phyllodes tumours is associated with histological features of malignancy but does not predict outcome.

Abstract

To study p53 protein expression in phyllodes tumours of the breast, with particular attention to its prevalence and to its relationship with histological features and clinical outcome. Stromal and epithelial p53 immunohistochemical expression was studied in 57 phyllodes tumours (27 benign, 17 borderline, 13 malignant) using an avidin-biotin peroxidase method. High levels of expression (> 30% of stromal nuclei) were found in eight phyllodes tumours (14%). p53 expression was associated with tumour grade (P = 0.001), prominent stromal overgrowth (P = 0.0003), prominent stromal nuclear pleomorphism (P = 0.006), high stromal mitotic count (P = 0.05), and an infiltrative tumour margin (P = 0. 05). Six patients were lost to follow-up after surgery. Mean follow-up time of the remaining 51 patients was 7.3 years (median 4. 3, range 0.5-25) or until death. Sixteen patients (31%) experienced tumour recurrence. Recurrence was more likely if there was an infiltrative tumour margin (P = 0.006) or prominent stromal overgrowth (P = 0.04) but not p53 expression (P = 0.55). A minority of recurrences expressed p53 more extensively than their primary counterparts. There were five tumour-related deaths (10% of patients). Death was associated with high grade (P = 0.0002), prominent stromal overgrowth (P = 0.0001), an infiltrative margin (P = 0.0002), prominent nuclear pleomorphism (P = 0.005), a high mitotic count (P = 0.01) and tumour size (P = 0.03). Again, p53 expression was not associated with tumour-related survival (P = 0. 13). p53 abnormalities occur in a minority of borderline and malignant phyllodes tumours. p53 expression is associated with known negative prognostic factors, but does not appear to be a useful determinant of tumour recurrence or long-term survival.