Breast cancer is a common malignant tumour prevalent in Ireland and rest of the world. Although breast cancer screening and treatment has dramatically improved patient prognosis, it is still the leading cause of cancer-related death for women. One of the major bases for breast cancer treatment is patient’s receptor status: ER, PR, HER2 positive or negative. Immunohistochemistry (IHC) is a technique that diagnoses abnormal cells, which uses antibodies to detect antigens (proteins) of interest in a biological tissue. IHC is widely used in hospitals and laboratories, for screening patient receptor status. In this study, IHC was performed on breast tumour samples obtained at Beaumont Hospital to assess 3 protein biomarkers Ki67, HOXC10 and HOXC11. Aim: This study aimed to use IHC technique to: 1. Optimize HOXC11 staining for use on TMA (Tissue MicroArray) 2. Assess Ki67 staining in a pre-stained TMA 3. Stain full face sections from primary and matched metastatic tissue for HOXC10.