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According to Centers for Disease Control, apart from non-melanoma skin cancer, breast cancer is the most common cancer among women in the United States. It is also one of the leading causes of cancer death among women of all races.

In 2011, an estimated 230,480 new cases of invasive breast cancer were expected to be diagnosed in women in the U.S., along with 57,650 new cases of non-invasive (in situ) breast cancer and researchers have been constantly working towards finding the factors that cause it. Nearly, 40000 deaths have been reported ever year. 

According to a latest study conducted at a commercial DNA testing service, women with larger breast size are more prone to developing breast cancer.

The study involved 16000 women participants, all of European Origin, who were asked to determine the cup size of their breasts between smaller than AAA and larger than DDD.

Earlier researches have linked more amount of non-fat tissue in the breasts to an increased risk of cancer but there wasn't any study linking cancer with breast size till date.

The scientists looked through the genetic code of the women participants and studied millions of tiny mutations in their DNA, called single-nucleotide polymorphisms.

The researchers found that the genetic mutations associated with breast size were also linked to the disease.

"Our results identify genetic variants that have an effect on both breast cancer and natural variation in breast size," said Dr Nicholas Eriksson of the California-based genetics firm 23andMe.

He added that this is the first substantial link between breast size and cancer. However, many more studies are needed before a cause and effect relationship can be established.

"It's fair to say that the link is a bit uncertain, and based on current knowledge, it's not a strong risk factor," Huffington Post quoted Eriksson as saying. He suggested that a simple explanation for the findings could be that larger breast size means more cells that could become cancerous.

But, he added, "part of the complication is that obesity also plays a complicated part in breast cancer risk."

A major drawback of the study is that the study has not considered the women's age, pregnancy and breastfeeding history and genetic ancestry.

Little is known about the biology of breast size, which scientists believe is only half hereditary, but high oestrogen levels are known to be a risk factor for breast cancer, reports Mail Online.

According to breast cancer specialist Dr. Edith Perez, deputy director at large at the Mayo Clinic Cancer Center (who was not involved in the 23andMe research), the researchers also did not include other risk factors in the study such as alcohol use and breast density.

Earlier studies have suggested that women with higher breast density are at five times higher risk of contracting the disease than others, however, the reason behind same is not clear.

"The way I look at it is that it's an interesting finding, but I do not think it will have a big impact on the way we stratify for risk for breast cancer," said Perez, adding that the research is done by a commercial company and that should be taken into consideration.

Eriksson emphasized that the research results may serve other researchers interested in the possible connection between breast size and cancer risk. But as for now, the size of the breast is not a "major factor," he explained.

"Breast size is definitely heritable," Eriksson said. "But unlike height, where you can look at both parents and get some idea how tall you will be, you have much less data for breast size. A young woman can look at her mom. However, she won't get the same insights by looking at her dad for his genetic contribution," Huffington Post reported.

The study was study published in the journal BMC Medical Genetics.