Is breast density related to cancer?

Doctors know that women with dense breasts have as much as six times the risk of breast cancer than those who have less dense breasts, but why that happens is yet to be explained.

However, a new research offers possible clues: Biopsies of healthy women showed differences in the cells of dense and non-dense tissue that may contribute to the development of tumors.

American doctors performed mammograms and biopsies on 60 women ages 45-85 with no history or symptoms cancer. The results showed that dense breast tissue was composed of 6 percent epithelial cells, which line the milk glands and ducts, compared to just 1 percent in the non-dense tissue. 64 percent of the dense tissue was made up of stroma (connective, non-functional supportive framework tissue), compared to 20 percent in the non-dense tissue. And dense tissue was comprised of 30 percent fat, versus 80 percent in non-dense tissue.


Breat tumors tend to originate in the epithelium, so having more of those cells may up a woman's risk of cancer. And areas surrounding the stroma produce growth factors that may stimulate the epithelium to turn cancerous. More expression of the aromatase enzyme, which converts the hormone androgen into estrogen, was found in the dense breast tissue. Estrogen drives most breast cancers, so drugs known as aromatase inhibitors are a common treatment choice.

If larger studies confirm their findings, doctors may be able to use density to determine how well such treatments are working.

Worldwide, breast cancer is the second most common type of cancer after lung cancer (10.4% of all cancer incidence, both sexes counted) and the fifth most common cause of cancer death. In 2005, breast cancer caused 502,000 deaths worldwide, almost 1% of all deaths.

Adapted from Scientific American Website

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