Primary mucinous ovarian neoplasms rarely show germ cell histogenesis.

Recently, genetic analyses of primary mucinous ovarian tumours (MOT) have considerably enhanced our understanding of the biology of such neoplasms, supporting a progressive model of carcinogenesis from benign/borderline tumours to carcinomas. Nevertheless, the histogenesis of these neoplasms remains a subject of discussion and several cell types of origin have been proposed; a proportion of these tumours are associated with Brenner (transitional cell) tumours, therefore some are believed to be derived from metaplastic mucinous epithelium lining cystic transitional cell nests (Walthard rests).