PCNA and breast cancer: Moreover, several additional biologic markers, such as angiogenesis, p53, proliferating cell nuclear antigen (PCNA), c-erbB-2, apoptosis, mitosis, and necrosis have been related to tumour proliferation and development, but their effects on tumour haematogenous metastasis are by no means clear, and there are still controversies regarding the best possible prognostic index for breast cancer patients (Thor et al, 1992; Gilchrist et al, 1993; Zhang et al, 1998; Kato et al, 1999; Beenken et al, 2001; Sirvent et al, 2001).