Validation of tissue microarray technology in endometrioid cancer of the endometrium

Aim: To validate tissue microarray (TMA) for endometrial cancer by comparing immunohistochemical staining results of triplicate core biopsies on TMA with the results of full-section analysis. Methods: The study material consisted of slides and selected tissue blocks of 41 patients with endometrioid cancer of the endometrium. A TMA was constructed. Both the TMA and the slides were stained with the same antibodies against progesterone receptor (PR), oestrogen receptor, p53 and epithelial membrane antigen (EMA). Concordance between results was expressed as the kappa statistic. Results: Concordance between the staining results of TMA and whole slides was good for PR (kappa = 0.69), oestrogen receptor (kappa = 0.78), p53 (kappa = 0.81) and EMA (kappa = 0.72). Concordance between the results on TMA and slides depends on the number of assessable cores per tumour. Three assessable cores per case result in outcomes that are at least 94% similar to those achieved using conventional tissue sections with a two-class scoring system. This is independent of focal or diffuse staining patterns. Conclusion: TMA is a useful tool for further analysis of the molecular pathways in endometrial cancer. The effect of selection has to be taken into account when the prognostic value of protein expression on TMA is determined.