Thymoma classification: current status and future trends.

The classification of thymic epithelial neoplasms has been a controversial topic for many years. Recent advances in diagnostic methods and renewed interest in the biology of these tumors has led to efforts by investigators to shed new light on their biologic behavior and to offer novel perspectives on these unusual neoplasms. Several new classification schemes have been proposed, including the new World Health Organization schema for the histologic typing of tumors of the thymus. We review the current status of thymoma classification and comment on problem areas and future trends that may offer a more pragmatic approach to these tumors.