Semi-quantitative scoring of potentially predictive markers for endocrine treatment of breast cancer: a comparison between whole sections and tissue microarrays

Aim: To assess whether immunohistochemically stained tissue microarrays ( TMA) of 2 mm cores from paraffin embedded tumour tissue may replace whole sections in semi- quantitative evaluation of selected potential markers for endocrine treatment. Methods: Whole sections and 2 mm cores on TMA were used for immunohistochemical staining of potential markers for endocrine treatment. The Allred scoring system was used for the markers with nuclear localisation: the oestrogen receptor, the progesterone receptor, p27 and the oestrogen receptor co- regulator amplified in breast cancer 1 ( AIB1). The Allred scoring system was also used for the non- nuclear markers Bcl2, pS2 and cyclooxygenase 2 ( COX- 2); the membrane receptors HER- 2, insulin- like growth factor 1 receptor ( IGF- IR) and epidermal growth factor receptor were quantified according to the guidelines for the Herceptest. Results: The data and statistical analyses showed that the semi- quantitative evaluation of oestrogen receptor, progesterone receptor, AIB1, COX- 2, HER- 2 and IGF- IR on TMA blocks was comparable with analysis on whole sections. Conclusions: This study shows that semi- quantitative scoring of 2 mm cores on TMA is feasible for several potential markers for endocrine therapy. Considering the small size of many breast tumours, the speed and cost- effectiveness of immunohistochemistry on TMA compared with whole sections, and the importance of the expression level of the proteins, semi- quantitative scoring on TMA has great potential in both retrospective and prospective studies aiming at improving the prediction of response to endocrine treatment.