There has long been a question as to whether there is a heightened risk of breast cancer due to the trauma caused by boxing. While not definitive, the leading answer from the medical community is simply that trauma to the breast is no more cause for cancer than a punch to a bicep or other soft tissue.
The American Cancer Society specifically states on their website that “…the fact is that falls, bruises, broken bones, or other such injuries have not been linked to cancer…” The ACS points out that sometimes existing cancer may be detected while a patient is being treated for an injury, but no actual link can be established that the injury caused the disease.
There is some reason for concern however. A somewhat controversial 2002 study showed that out of a group of about 200 women, 1/3 of which had breast cancer and 2/3 did not, the women who had breast cancer were more likely to report a physical trauma to the breast within the previous 5 years. The conclusion of the study was that a link between the trauma and the cancer was possible. Unfortunately, due to the size of the study the conclusion is easy to discount. It is also worth noting that a much older study exists showing that injuries in experimental animals were apparently no cause for cancer.
While, for now, trauma from a punch appears to not be a direct cause of cancer there is evidence that supports the idea that trauma to an area of the body already afflicted with cancer could increase the growth rate of the disease. There are also separate studies showing possible links between trauma and bone cancer and multiple abrasions and skin cancer.
The idea of physical trauma causing cancer is an ongoing debate, however there doesn’t appear to be significant cause for concern that a woman who boxes is any more at risk than other women.