Endometriosis increases the risk of certain cancers according to a recent analysis by Dr Anna-Sofia Melin at the Karolinska University Hospital in Stockholm, Sweden. About 63,000 women who had been given a diagnosis of endometriosis between 1969 and 2002 were identified. In endometriosis, cells that usually only grow within the uterus grow outside the uterus.

The researchers found that endometriosis increased the risk of developing ovarian cancer by more than a third above the risk for women who did not have endometriosis (37%). There were similar increases in risk for endocrine tumours (38%), kidney cancer (36%) and thyroid cancer (33%). Slightly lower increases were found for brain tumours (27%) and malignant melanoma (23%), and there was a small increased risk of breast cancer (8%). In contrast, women with endometriosis had a reduced risk of cervical cancer of just under a third (29%).

However, there was no difference found between the risk of cancer in women with endometriosis who had borne children versus those who had not.

Dr. Melin cautions that it is too early to use the results of this study to give advice to doctors, but she stated, "Our hope is that doctors in general start to view the endometriosis disease as a serious disease that causes a lot of suffering to the patient and also may lead to cancer. We hope that in the future we will be able to identify those women with endometriosis that may have a more aggressive form of disease with more atypical cells, for instance, and that this may lead to better care for the patient and, hopefully, to a early diagnosis if cancer should occur."