Lateral distribution of nonendometriotic benign ovarian cysts

To investigate the left- and right-sided distribution of nonendometriotic benign ovarian cysts, data were collected on 406 women undergoing first-line surgery for tumours with various histotypes. Considering the unilateral cysts, the observed proportion of left lesions was 65/129 (50.4%) in the serous, 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, without significant differences from the expected 50%. This contrasts with the finding of a significantly more frequent development of endometriomas on the left ovary, and suggests that the pathogenesis of endometriotic and nonendometriotic cysts is different.