Ovary: Benign Epithelial Neoplasms

Abstract

The epithelial group of ovarian tumours accounts for 60% of all primary neoplasms of the ovary. All are thought usually to originate from cells in the surface epithelium of the ovary, either arising directly from that epithelium or from epithelial fragments sequestrated into the ovarian cortex to form inclusion cysts1. The ovarian surface epithelium is the adult equivalent, and direct descendant, of the coelomic epithelium which, during embryonic life, overlies the nephrogenital ridge, and from which are derived the Mullerian ducts and the structures to which these give rise. It is believed that undifferentiated cells in the surface epithelium of the postnatal ovary retain a latent capacity to differentiate along the same pathways as do their embryonic precursors, and hence a neoplasm derived from these cells can differentiate along various Mullerian pathways, those differentiating along tubal epithelial lines forming the serous group of neoplasms, those following an endocervical route being the mucinous tumours and those differentiating along an endometrial pathway forming the endometrioid group of neoplasms. The Brenner tumour usually originates from the surface epithelium but is, however, non-Mullerian in nature for the epithelial component of these neoplasms is identical with uroepithelium2: this indicates that cells in the surface epithelium also have a residual capacity for Wolffian differentiation, a not surprising potentiality in view of the close embryological relationships between Wolffian and Mullerian systems. The mesonephroid group of tumours, so called because of a historical misinterpretation of their origin, is still of slightly controversial nature; many, probably most, are of Mullerian type3 and represent a variant form of endometrial differentiation, but it remains possible that some are mesotheliomata4: it should be remembered in this respect that all these neoplasms, derived as they are from serosa, are in essence mesotheliomata though their true nature is usually concealed by various degrees of Mullerian or Wolffian differentiation. Certainly a true mesothelioma can, very rarely, develop from the ovarian surface epithelium5.