PT Journal AU Klapper, W Hoster, E Determann, O Oschlies, I van der Laak, J Berger, F Bernd, HW Cabeçadas, J Campo, E Cogliatti, S Hansmann, ML Kluin, PM Kodet, R Krivolapov, YA Loddenkemper, C Stein, H Möller, P Barth, TEF Müller-Hermelink, K Rosenwald, A Ott, G Pileri, S Ralfkiaer, E Rymkiewicz, G van Krieken, JH Wacker, HH Unterhalt, M Hiddemann, W Dreyling, M TI Ki-67 as a prognostic marker in mantle cell lymphoma—consensus guidelines of the pathology panel of the European MCL Network SO Journal of hematopathology PY 2009 BP 103 EP 111 VL 2 IS 2 PU Springer Science and Business Media LLC DI 10.1007/s12308-009-0036-x WP https://macau.uni-kiel.de/receive/macau_mods_00002119 LA en SN 1868-9256 AB Mantle cell lymphoma (MCL) has a heterogeneous clinical course and is mainly an aggressive B cell non-Hodgkin lymphoma; however, there are some indolent cases The Ki-67 index, defined by the percentage of Ki-67-positive lymphoma cells on histopathological slides, has been shown to be a very powerful prognostic biomarker. The pathology panel of the European MCL Network evaluated methods to assess the Ki-67 index including stringent counting, digital image analysis, and estimation by eyeballing. Counting of 2 × 500 lymphoma cells is the gold standard to assess the Ki-67 index since this value has been shown to predict survival in prospective randomized trials of the European MCL Network. Estimation by eyeballing and digital image analysis showed a poor concordance with the gold standard (concordance correlation coefficients [CCC] between 0.29 and 0.61 for eyeballing and CCC of 0.24 and 0.37 for two methods of digital image analysis, respectively). Counting a reduced number of lymphoma cells (2 × 100 cells) showed high interobserver agreement (CCC = 0.74). Pitfalls of the Ki-67 index are discussed and guidelines and recommendations for assessing the Ki-67 index in MCL are given. PI Berlin ER