title: Endometriosis and ovarian cancer risk: a systematic review of epidemiological studies.
abstract: BACKGROUND
  A possible etiological association between endometriosis and ovarian cancer has been repeatedly reported in the literature.
  
  
  OBJECTIVE
  Our aim was to evaluate published epidemiological data on this issue.
  
  
  METHODS
  We conducted an extensive search of the literature in MEDLINE, of articles ever published until February 2014, using the key-words "endometriosis" and "ovarian" and one of the following terms in the title: "cancer" or "malignancy" or "malignant" or "tumor" or "neoplasia" or "neoplasm" or "transformation." Retrieved papers were checked for further relevant publications.
  
  
  RESULTS
  Overall, our search yielded 1 prospective cohort study, 10 retrospective cohort, and 5 case-control studies. A meta-analysis of these studies was not considered to be appropriate, due to differences in data reporting, study design, and adjustment for confounding factors.
  
  
  CONCLUSIONS
  The main limitation of studies found, with one exception, was the lack of operative confirmation of endometriosis.
  
  
  CONCLUSIONS
  An association of endometriosis with clear-cell and endometrioid ovarian cancer was a consistent finding in most studies. On the other hand, existing epidemiological evidence linking endometriosis with ovarian cancer is insufficient to change current clinical practice. Prospective cohort studies, with prior laparoscopic confirmation, localization, and staging of endometriosis are needed, in order to further clarify this issue.
authors.affiliation: 1st Department of Obstetrics and Gynecology, Medical School, Aristotle University of Thessaloniki , Thessaloniki , Greece ; School of Health and Medical Care, Alexander Technological Educational Institute of Thessaloniki , Thessaloniki , Greece.
authors.forename: Menelaos
authors.initials: M
authors.lastname: Zafrakas
authors.affiliation: 1st Department of Obstetrics and Gynecology, Medical School, Aristotle University of Thessaloniki , Thessaloniki , Greece.
authors.forename: Grigorios
authors.initials: G
authors.lastname: Grimbizis
authors.affiliation: 1st Department of Obstetrics and Gynecology, Medical School, Aristotle University of Thessaloniki , Thessaloniki , Greece.
authors.forename: Anna
authors.initials: A
authors.lastname: Timologou
authors.affiliation: 1st Department of Obstetrics and Gynecology, Medical School, Aristotle University of Thessaloniki , Thessaloniki , Greece.
authors.forename: Basil C
authors.initials: BC
authors.lastname: Tarlatzis
keywords: causal association; endometriosis; ovarian cancer; ovarian neoplasia; ovarian tumor