- Paper Report
- Open Access
Tissue microarray validation
- Valerie Speirs1
© Biomed Central Ltd 2001
- Received: 5 March 2001
- Accepted: 20 August 2001
- Published: 1 December 2001
- Archive, breast cancer, tissue microarray
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.
Most cases had at least six out of ten scorable cores. These were considered scorable if at least 10% of the core area contained tumour. Based on whole section staining, the percentage of ER, PR and Her2/neu positive sections was 68%, 56% and 24% respectively. Analysis of ER and PR by microarray showed agreement in 35 out of 36 cases (ER) and 34 out of 35 (PR). Her2/neu expression showed more variability but the average staining correlated with that of the whole section. Overall, analysis of two microarray cores was comparable to that of a whole tissue section showing 95% concordance. To ensure adequate representation of the tumour, a total of three cores from a cross section of the block should be taken. Archival material dating from 1932 was also suitable for this technique with, in general, no real changes in antigen expression over time for ER, PR, Her2/neu, Ki67 and cytokeratin.
Archival material from 1932-1999 was selected from 38 cases of invasive breast cancer. Tissue areas corresponding to invasive carcinoma and normal epithelium were identified by hematoxylin and eosin staining and 10 core biopsies taken from each area (five from the periphery and five from the centre). Cores were transferred to a recipient masterblock. Sections were prepared from both the original block and the arrayed block and stained for ER, PR, Her2/neu, Ki67 and cytokeratin using standard immunohistochemical techniques. The results were analysed and compared.
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