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Individuals with Lynch syndrome, a genetic condition that has long been known to carry dramatically increased risk of colorectal cancer and uterine cancer, now also have an increased risk of breast cancer. This is the conclusion of a study in the journal Genetics in Medicine.

Lead author Maegan Roberts and researchers at the company GeneDx and Columbia University suggest that women who carry the particular genes responsible for Lynch Syndrome, known as MSH6 and PMS2, may benefit from more intensive breast cancer screening.

Lynch syndrome is common in the general population estimated to affect one in 370 people globally. Individuals reporting a personal or family history of colorectal and uterine cancers are often tested for these genes. However, genetic tests are generally not included when breast cancer is the predominant cancer in a family.

Roberts and her colleagues reviewed the GeneDx database of more than 50000 adult women who had undergone genetic testing between 2013 and 2016. Of these, 423 women tested positive for a variant of the four MMR genes. The researchers compiled the cancer history of these women and their family members.

Researchers found that women who possessed two variants of MMR genes called MSH6 and PMS2 had a two-fold or three-fold increased risk of developing breast cancer, while no breast cancer association was observed for two of the other variants. One in every four of the 423 women reported a history of breast cancer, first diagnosed at an average age of