The New World Health Organization (WHO) classification of ovarian tumors: A commentary

The basic structure of the new (1999) WHO classification of ovarian tumors differs only slightly from that of the previous (1973) system. The impact o f new research findings is limited, particularly regarding epithelial borde rline tumors (tumors of low malignant potential), so that this diagnostic g ray zone persists. The new classification has added a large number of rare and sometimes imprecisely defined tumors. For example, the very extensive s ubclassifications of certain groups of tumors (for example, nine types of m onodermal teratomas) is not conducive to clarity or reproducibility and of questionable clinical relevance. Immunohistochemical methods and molecular pathology could have contributed to a clearer and in some cases more precis e classification. Nonetheless the new WHO classification should be used as the international standard.