Nomenclature Evolution: Changes in the ISCN from the 2005 to the 2009 Edition

The Committee for the International System for Human Cytogenetic Nomenclature (ISCN) has recently met and published a revised version, ISCN 2009. Multiple changes in nomenclature guidelines are presented in that updated version. This review will highlight changes to the idiograms and specific changes in respective chapters of the 2009 version compared with the previous version of the ISCN published in 2005. These highlights are meant as a guide for the cytogeneticist to assist in the transition in the use of this updated nomenclature for describing cytogenetic and molecular cytogenetic findings in both clinical and research reports.