Altered expression of p53 and its regulated proteins in phyllodes tumours of the breast

The histological characteristics of phyllodes tumours of the breast are often not related to their clinical outcome. Additional studies must therefore be performed to investigate the possible relationship of cell biological parameters to the biological behaviour of these tumours. The expression of Ki-67, p53, and its regulated proteins has been studied in 19 primary phyllodes tumours, from patients with known follow-up, using immunohistochemical and molecular biological techniques. Overexpression of the p53 protein was observed in four cases and mutation in two cases. In only one case, the sequence alteration, at codon 273, was associated with overexpression of p53 protein and with strong expression of Ki-67 (30 per cent). This alteration was found in the primary, the recurrent, and the metastatic tumour samples. Moreover, the same p53 gene mutation, Arg273Cys, was detected in all tumour samples. No mutation was found in adjacent normal breast tissue, indicating that this was an acquired mutation. Unexpectedly, strong BAX expression was observed in the primary tumour. The patient died during the follow-up period. It is concluded that p53 gene status and an accumulation of BAX, both involved in the same apoptosis-controlling pathway, may be of prognostic relevance in phyllodes tumours.