Immunohistochemical analyses of CA IX on TMAs. The tissue microarrays (TMAs) were scored by two observers: observer 1 (Obs. 1) and observer 2 (Obs. 2). Only tumours that were interpretable on all four cores were included in this analysis. The left-most bar in each group (TMA 1) gives the frequency of tumour positivity in one TMA core. The subsequent bars (moving from left to right) show the tumour positivity observed after adding information from addtional cores.