The World Health Organization (WHO) histologic classification of thymomas: a reanalysis

Abstract

The histologic classification of thymomas has remained for many years an area of conflict. In recent years, the World Health Organization (WHO) presented a proposal for the classification of these tumors, which has been widely adopted in many countries throughout the world. Two successive versions of this classification have been presented in recent years; however, controversy still exists regarding its accuracy and usefulness in clinical practice. We present a review of the current WHO classification of thymomas, with a discussion of some of the inconsistencies and limitations and the possible alternatives to the current approach for the histopathologic classification of these tumors.