Association between endometriosis and cancer : a comprehensive review and a critical analysis of clinical and epidemiological evidence

Objective.: This review was aimed to critically evaluate observational, cohort, and case-control studies performed so far in order to assess the association between endometriosis and malignant diseases. Based on the observations herein presented, clinical indications that might avoid physicians' mismanaging of affected patients are proposed. Methods.: Search strategies included online searching of the MEDLINE database and hand searching of relevant publications and reviews. Additional reports were collected by systematically reviewing all references from retrieved papers. Results.: Endometriosis is not associated with an increased risk of cancer in general. Data from large cohort and case-control studies indicate an increased risk of ovarian cancers in women with endometriosis. The observed effect sizes are modest varying between 1.3 and 1.9. Evidence from clinical series consistently demonstrates that the association is confined to the endometrioid/clear-cell histotypes. Available studies are characterized by several limitations, some of which potentially bias results towards the null hypothesis whereas others leading to overestimate the association. Evidence for an association with melanoma and non-Hodgkin's lymphoma is increasing but still to be verified whereas an increased risk for other gynecological cancer types is not supported. Conclusions.: Epidemiological findings on the association between endometriosis and cancer are still elusive. At present, endometriosis should not be considered a medical condition associated with a clinically relevant risk of any specific cancer. On the basis of the present findings, modifications of the standard treatment options for the disease are not justifiable.