Estimation of EBER expression level with spline curve. (A) Four-level semiquantitative estimation of different levels of EBER expression, quoted from 0 (EBER-ISH negative) to 4. Examples are shown at original magnification ×100 (top row) and ×200 (bottom row). Images were captured with a Zeiss Axioskop2 microscope (Zeiss, Oberkochen, Germany) and Neofluar 100×/0.1 NA optical lenses (Zeiss). Photographs were taken with a DP70 Olympus camera (Olympus, Tokyo, Japan). Image acquisition was performed with Olympus DP Controller 2002, and images were processed with Adobe Photoshop v7.0 (Adobe Systems, San Jose, CA). (B) The spline curve shows how the relative risk of death changes with the level of EBER positivity. The dotted lines show the 95% confidence interval. Bold lines show the best cut-off point.