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

Aims: To study p53 protein expression in phyllodes tumours of the breast, w ith particular attention to its prevalence and to its relationship with his tological features and clinical outcome. Methods mid results: Stromal and epithelial p53 immunohistochemical express ion was studied in 57 phyllodes tumours (27 benign, 17 borderline, 13 malig nant) using an avidin-biotin peroxidase method. High levels of expression ( > 30% of stromal nuclei) were found in eight phyllodes tumours (14%). p53 e xpression was associated with tumour grade (P = 0.001), prominent stromal o vergrowth (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-u p 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. Rec urrence was more likely if there was an infiltrative tumour margin (P = 0.0 06) 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 patient s), Death was associated with high grade (P = 0.0002), prominent stromal ov ergrowth (P = 0.0001), an infiltrative margin (P = 0.0002), prominent nucle ar pleomorphism (P = 0.005), a high mitotic count (P = 0.01) and tumour siz e (P = 0.03). Again, p53 expression was not: associated with tumour-related survival (P = 0.13). Conclusions: p53 abnormalities occur in a minority of borderline and malign ant phyllodes tumours. p53 expression is associated with known negative pro gnostic factors, but does not appear to be a useful determinant of tumour r ecurrence or long-term survival.