The oncogenic capabilities of cyclin D1 in a breast cancer setting have been well established. Amplification of the CCND1 gene is consistently associated with reduced patient survival times and treatment resistance. However, repeated attempts to clarify the prognostic impact of the cyclin D1 protein in breast cancer have yielded contrasting results. As such, the primary objective of my research is to remove all ambiguity surrounding the prognostic potential of cyclin D1 protein in breast tumours, thus promoting its use as a clinically relevant biomarker. Secondary to this, I aim to further understand the complex relationship between cell cycle and cell proliferation from a clinically orientated perspective by combining gene expression/pathology based technologies for the prognosis of primary breast tumours.