Context
For well over a century, pathologists have used formalin-fixed paraffin-embedded tissues for microscopic examination and subsequent diagnosis of human disease. This type of approach is usually limited to the analysis and/or detection of one or two specific features on a single slide from an individual section. The recent development of tissue microarrays (see Additional information) involves core needle 'biopsies' of multiple pre-existing paraffin-embedded tissue blocks and re-embedding them in the form of an arrayed master block. Thus, tissue from an entire cohort of specimens can be represented in a single block and processed under identical conditions. This study evaluated the potential of using tissue microarrays of archival formalin-fixed paraffin-embedded breast tumours to detect expression of three common antigens in breast cancer: estrogen receptor (ER), progesterone receptor (PR) and Her2/neu.