Lateral distribution of nonendometriotic benign ovarian cysts

To investigate the left- and right-sided distribution of nonendometriotic b enign ovarian cysts, data were collected on 406 women undergoing first-line surgery for tumours with various histotypes. Considering the unilateral cy sts, the observed proportion of left lesions was 65/129 (50.4%) in the sero us, 38/79 (48.1%) in the mucinous, 59/134 (44.0%) in the dermoid, 11/21 (52 .4%) in the parovarian, and 3/7 (42.9%) in the miscellaneous cysts group, w ithout significant differences from the expected 50%. This contrasts with t he finding of a significantly more frequent development of endometriomas on the left ovary, and suggests that the pathogenesis of endometriotic and no nendometriotic cysts is different.