Ovarian endometriotic cysts. An analysis of cytologic atypia and DNA ploidy patterns.

Cytologic atypia may be seen in the glandular epithelium that lines ovarian endometriotic cysts. The significance of this atypia has not been fully elucidated. The authors studied the morphologic appearance and DNA ploidy of the glandular epithelium from 36 ovarian endometriotic cysts by image analysis on formalin-fixed paraffin-embedded tissue sections. In 29 of the cases the corresponding endometrium proper also was studied. The DNA content was diploid in all eutopic endometrium and in the lining epithelium of all endometriotic cysts without atypia or with only mild cytologic atypia. DNA aneuploidy was observed in 3 of 6 endometriotic cysts with severe atypia. Our findings indicate that mild cytologic atypia in the glandular epithelium of endometriotic cysts is associated with normal DNA ploidy patterns, whereas severe atypia may be associated with aneuploidy. These findings support the hypothesis that cytologic atypia represents the precursor lesion for the invasive epithelial malignancy that may arise in ovarian endometriotic cysts.