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Women Maintaining Younger-Looking Breasts

Can Make Mammograms More Difficult to Read

WebMD Health News

March 17, 2004 (Hamburg, Germany) -- A new study shows that women today are maintaining younger-looking "dense" breast tissue beyond menopause -- potentially making mammograms more difficult to read and leading to unnecessary biopsies.

Generally, women's breasts become less dense as they age -- meaning more fatty tissue. This change makes breast abnormalities such as tumors more visible on mammograms. But researchers are now seeing that this change in breast tissue isn't occurring in some women.

Maintaining denser breast tissue may be due to changes in childbearing patterns -- women starting their families later or not having children at all -- according to researcher Fred van der Horst, MD. Women who have given birth develop more fatty breast tissue than childless women, the researchers say.

The findings were presented here at the 4th European Breast Cancer Conference.

The researchers analyzed a random sample of 2,000 screening mammograms from women in a regional screening program in the Netherlands. They categorized breasts as dense if more than 25% of the tissue had a dense pattern and clear or "lucent" if such tissue constituted less than 25% of the breast.

Surprisingly, one-fourth of the women 50 to 69 years old had a dense breast pattern on their mammograms.

Denser Breast Hinders Mammogram

The researchers also found that mammograms were less accurate at detecting breast cancers in women with denser breast tissue. In women with dense breast tissue, only 59% of those who had had cancer were accurately diagnosed by mammography. In women with less dense breast tissue, mammograms accurately detected 67% of breast cancers.

Although menopausal hormone therapy may contribute to an increase in breast tissue density, van der Horst says the new breast tissue patterns could not be solely attributed to the women's use of hormones. Less than 10% of perimenopausal women used hormones, and hormone use was almost nonexistent in the elderly, he says. Van der Horst is a radiologist at the National Training and Reference Center in Nijmegen, Netherlands.

He stresses that women should still get mammograms, though. "It's the only form of breast cancer screening with proven effect."

"The Dutch study confirms our findings," says Caroline E. Blane, MD, who conducted a separate mammogram study. She is a professor of radiology at the University of Michigan in Ann Arbor. "The breast tissue stays denser [for a longer time] in women today than in previous times. With more of the denser breast tissue, screening mammography becomes more difficult."

Therefore, for women with this type of breast tissue pattern, the routine mammography could become less routine, she says. "Patients will more often need a second diagnostic mammogram." As many as 10% of women may need follow-up studies, a practice that will drive up the cost of mammography."

"The science shows that mammography reduces the risk of breast cancer mortality if done consistently," says Lawrence D. Wagman, MD, chairman of the division of surgery at City of Hope Cancer Center in Duarte, Calif. The density issue is yet another reason that women should have their mammograms and breast exams overseen by thorough physicians who take all factors into account, he says.

"The study doesn't take away from mammogram's value as a screening tool," provided that all of the information is considered, he says. "The most dangerous [choice] would be for the physician not to pursue a finding, such as a lump, just because the imaging study is negative."

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