Cancer-related mutations have been found in tissue taken from patients with deep endometriosis.
The findings are surprising as deep endometriosis is not associated with an increased risk of cancer, and open new possibilities for diagnosis and treatment.
'These mutations are a first step in understanding the breadth of symptoms and outcomes that affect every patient differently. Finally, we have a roadmap to find the right treatments,' said co-author Dr Michael Anglesio at the University of British Columbia in Canada.
Endometriosis is a condition where the tissue lining of the womb grows out into nearby regions of the body, causing lesions, pelvic pain and menstrual abnormalities. It occurs in up to ten percent of pre-menopausal women.
The team, from the University of British Columbia, and Johns Hopkins Medicine, Maryland, sequenced the exome of normal tissue and endometrial tissue of 24 women from Japan and New York City. They found that 19 out of 24 tested tissue samples had one or more mutations in the endometrial tissue that were not present in the normal tissue of the patients.
The most common mutations were in genes linked to ovarian cancer, including ARID1A, PIK3CA, KRAS and PPP2R1A, all known for regulating cell growth, cell invasion and DNA repair. Looking specifically for mutations in the KRAS gene, which is involved in cell growth and replication, they found mutations in five of an additional 15 women with endometriosis.
The findings also challenge the theory that endometriosis occurs when normal endometrial tissue leaks into the abdominal cavity during menstruation. Instead, the scientists say that endometriosis could occur if normal endometrial cells acquire mutations which change their function.
However, endometrial tissue rarely becomes cancerous except in a few cases when the disease occurs in the ovaries.
'We don't yet understand why these mutations occur in these tissues, but one possibility is that they could be giving the cells an advantage for growth and spread,' said co-author Nickolas Papadopoulos, professor of oncology at Johns Hopkins Medicine.
The scientists say the findings could be used to develop tests to distinguish between non-aggressive and aggressive types of endometriosis. According to co-author Dr Paul Yong at the University of British Columbia, the study could have wider implications.
'[Scientists] need to learn more, through a bigger, longer study, about what puts the brakes on [mutations associated with cancer], especially if there are certain 'micro-environments' that hinder the transformation of growths from being merely abnormal to becoming malignant,' he said to endometriosis.org.