Researchers in the US have identified two new genes associated with breast cancer: MSH6 and PMS2.

The new study suggests that each gene approximately doubles a woman’s risk of developing breast cancer by age 60. The two genes were previously known to cause Lynch syndrome, an inherited condition that raises the risk of colorectal, ovarian, stomach, and endometrial cancer.

This study shows that some women with Lynch syndrome are also more likely to develop breast cancer.

The researchers analysed a database of more than 50,000 women who had undergone multi-gene hereditary cancer testing between 2013 and 2015. Of these, 423 women had a mutation in one of the four genes that cause Lynch syndrome: MLH1, MSH2, MSH6, and PMS2.

Further analysis revealed that women with a mutation in two specific Lynch syndrome genes—MSH6 and PMS2—had a two-fold higher risk of breast cancer compared to women in the general population.

Based on the incidence of cancer in the study population, the researchers calculate that up to 38 percent of women with cancer-causing MSH6 and PMS2 variants will develop breast cancer, compared to around 15 percent of women in the general population.

Women with a family history of breast cancer often undergo genetic testing for mutated BRCA1 and BRCA2 genes, which increase the risk of breast cancer over a woman’s lifetime to between 50 and 60 percent.

Researchers involved with the new study say their findings suggest that MSH6 and PMS2 should be added to the list of genes to screen for when there is a history of breast cancer.

Currently, testing for Lynch syndrome genes is generally only done when someone has a personal or family history of colon or uterine cancer.

4 April 2018

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