Endometrioid neoplasia of the ovary: a reappraisal

The emergence in recent years of new concepts and entities pertaining to ovarian endometrioid neoplasia has led to a reappraisal of the subject. In this reappraisal, the double listing of benign endometrioid lesions as both "tumors" and "tumor-like" lesions, as it appears in the World Health Organization (WHO) classification, is being avoided and they are all listed under one heading. Clear cell tumors, which, in the WHO classification, are not listed under endometrioid neoplasia, are included among the latter in the proposed classification. Recently described entities are reviewed, as are those previously listed but not well documented. Some of the WHO listed endometrioid tumors of low malignant potential are omitted from the present discussion, as histologic and clinical data pertaining to such neoplasms are still not available.