Breast Density and Cancer

        Breast Density and Cancer

I always had very lumpy breasts, that also showed lots of whitish tissue in mammograms. Back in 1999 my doctor reassured me that this is not a risk factor for breast cancer.  But our knowledge has changed dramatically since [1] and according to Cancer Care Ontario, the Ontario government’s principal adviser on cancer, breast density is one of the strongest risk factors for breast cancer, as strong as family history!

            What is breast density?  All breasts contain milk glands and ducts, fat, and fibrous connective tissue. “Fibroglandular tissue” refers to glands and ducts and fibrous tissue. Breast density is determined by the relative amount of fibroglandular tissue (dense) and fat (not dense). There are 4 categories of breast density that range from fatty breasts to extremely dense breasts. Women with over 50% dense tissue are considered to have dense breasts. The density cannot be felt by the woman or her doctor. Only a mammogram can tell.

Why does it matter if you have dense breasts?

Dense breasts pose two risks:

1.  On a mammogram, dense breast tissue appears white and so does a cancerous mass, creating a masking effect that makes it difficult for the radiologist to detect cancer.  Fatty breasts on the other hand appear dark on a mammogram and since cancer appears white, it is easy to spot cancer (see Figure below).

2.   Having dense breasts increases breast cancer risk. Women in the highest category of density are 4-6 times more likely to get breast cancer than those with fatty breasts.

Dense breasts are common. About 43%women undergoing mammograms have dense breasts. Younger or slim women or women taking hormones after menopause are more likely to have dense breasts. Breast density usually decreases with age.

What information is given to women in Ontario with dense breasts?

After a mammogram, patients in the Ontario Breast Cancer Screening Program aged 50-74 receive a report in the mail with their results. Women with breast density over 75% are sent a letter a year later asking them to return for a mammogram, as opposed to every two years for women of average risk. The level of the patient’s breast density is ticked off as under 75% or over 75% on the healthcare practitioner’s report.  If the breast density falls between 50- 75%, which is considered dense breasts, women in Ontario are not informed. Neither are their doctors. Annual mammograms for women with over 75% density are an issue since studies show about 50% of breast cancers are missed by mammograms in this category [2].

            Dense Breasts Canada (DBC), a group of breast cancer survivors and health-care providers dedicated to raising awareness about breast density, is also advocating for mandatory notification of breast density across the country to both patients and their doctors.  There are varying degrees of notification across the country. DBC is also advocating for screening ultrasound for patients with greater than 75 per cent breast density. Currently, screening ultrasound, which is less susceptible to masking effects, is not part of the Ontario provincial screening program. However, in BC and AB, it is paid for by the provincial programs.

            According to Radiologist Dr. Paula Gordon, a University of British Columbia clinical professor and medical adviser to Dense Breasts Canada, women should be notified of this risk factor. Knowing the level of their breast density allows women to be proactive: they can take better care of themselves, conduct self-exams more regularly, exercise, and try to mitigate risk factors such as weight and alcohol use. Above all, be aware that an all clear mammogram may not be accurate if they have dense breasts.

            Dr. Martin Yaffe, a University of Toronto professor and cancer researcher at Sunnybrook Health Sciences Centre who has been studying breast density for 25 years and helped develop Ontario’s breast screening guidelines, said the province should develop guidelines for supplementary screening, including testing with ultrasound or MRI. He said that since mammograms tend to be less accurate at detecting cancers in women with dense breasts, doing them more frequently is not the answer. Yaffe suspects that the cost of supplementary screening may have something to do with the province’s reluctance to make additional testing part of the protocol. Right now, the only way for a patient to have additional screening is for them to “push” for it, he said.

            I have to add my own story: I was diagnosed with breast cancer, just 11 months after a mammogram that came out as “normal”.  It was of a “pleomorphic lobular” pathology, described in the literature as a “particularly lethal variant”. I am left to wonder if an ultrasound might have caught it earlier, at the in situ stage…

            A new method coming from Japan is using radiofrequency waves and is capable of clearly detecting tumours. It does not require compression of the breast and is free from radiation exposure. It will be available in a few years.

Leda Raptis, May 20, 2019

[1].  Engmann et al. Population-Attributable Risk Proportion of Clinical Risk Factors for Breast Cancer

JAMA Oncol. 2017;3(9):1228-1236.

[2].  Kolb et al. Comparison of the performance of screening mammography, physical examination, and breast US and evaluation of factors that influence them: an analysis of 27,825 patient evaluations. Radiology. 2002 225:165-75.

Read on…

Her dense breast tissue hid cancer for years. Now she’s warning others

Fibrous breast tissue can obscure or camouflage cancer in mammograms

CBC Radio · September 14

Michelle Di Tomaso is co-founder of Dense Breasts Canada, a group that spreads awareness about how breast density can affect women’s health. (Submitted by Michelle Di Tomaso)


Listen to the full episode26:29

In 2014, Michelle Di Tomaso was diagnosed with advanced breast cancer. It came as a shock to her because she had undergone four clear mammograms.

She was devastated to learn that the tumour in her left breast had been growing for two to three years.

She believes she might have caught it earlier if she knew one thing: she has dense breasts.

But Di Tomaso didn’t discover that until after undergoing an ultrasound and a biopsy.

“It was a camouflage effect, and they missed it. I said, ‘They missed it for three f–king years?’ And [the medical oncologist’s like, ‘It happens,'” Di Tomaso recalled to White Coat, Black Art’s Dr. Brian Goldman.

Following the discovery, she underwent rounds of chemotherapy and radiation, a double mastectomy and a raft of complications.

Dense breast tissue can obscure cancer in a mammogram image. (Submitted by Dense Breasts Canada)

Breast density has been known in the medical community for decades, but it’s still a relatively unknown issue to family doctors and patients, in part because physicians aren’t instructed to tell their patients about it.

While fatty tissue appears as dark grey in a mammogram, dense tissue shows up as mostly white — just like cancers.

In 2016, Di Tomaso co-founded Dense Breasts Canada, a non-profit group which raises awareness about breast density and lobbies to make it easier for patients to find out if they have dense breasts.

“I want a woman to be told her breast density when she has a mammogram … If that woman has dense breasts, I want her to have an ultrasound,” she said.

Nearly half of U.S. women have dense breast tissue

Despite the name, dense breasts don’t feel any different to the touch. Only a mammogram can identify whether someone’s breast tissue is denser than average.

Over 40 per cent of women, aged 40 to 74, have some degree of dense breast tissue, according to a 2014 U.S. study.

It’s like somebody having high blood pressure and not telling them. No family doctor would do that.– Dr. Paula Gordon

Dr. Paula Gordon, Dense Breasts Canada’s medical adviser, says she often sees women with dense breasts who have had their cancer missed by a mammogram.

“This is where the anger comes from,” she said. “They were never told they had dense tissue, and so they didn’t realize there was this huge difference in the sensitivity of mammography depending on how dense the breast tissue is.”

Gordon, who is the medical director of the Sadie Diamond Breast Program at B.C. Women’s Hospital, added that cancer is “four to six times more common” in women with the highest breast tissue density, but researchers don’t know why.

In 1986, the BC Cancer Agency became the first provincial agency to do screening mammograms. From the very beginning, radiologists were asked to indicate on each mammogram if the woman had dense breasts and so they did.

But there wasn’t a directive to tell patients.

“It’s like somebody having high blood pressure and not telling them. No family doctor would do that,” Gordon said.

“When I raised it at a committee and said, ‘Why aren’t we telling them?’ they said, ‘We don’t want to make women anxious.'”

I will take that little bit of anxiety to find out it’s OK, than not knowing and then being told I have cancer.– Michelle Di Tomaso

Di Tomaso was “very insulted” when she first heard that reasoning. 

“I will take that little bit of anxiety to find out it’s OK, than not knowing and then being told I have cancer — just because you guys don’t want to tell us. Because of ‘anxiety.'”

Gordon wants women to start going for mammograms closer to the age of 40, which she calls “the ideal age to start screening.”

That way women can find out sooner whether they have dense breasts. If they do, they can be screened with an alternative method, such as an ultrasound or MRI to check for potential cancers.

Currently, the Canadian Task Force on Preventive Health Care recommends women have a mammogram every two years starting at age 50.

Updating guidelines for patients

Quebec is the only province that requires a woman’s breast density information be given to her family doctor.

In other provinces, doctors might be given the info from a mammogram report, but they aren’t required to inform patients.  What good is it? 

In New Brunswick, where an election campaign is currently underway, both Liberal and Progressive Conservative leaders pledged to ensure women are notified of their breast density.

            The discussion there has been spearheaded by breast cancer survivor Kathy Kaufield, who has been promoting breast density awareness with her #TellMe social media campaign.

In Prince Edward Island, Health PEI is planning to look at how and when patients are given breast density information as part of an upcoming review of their breast cancer screening program.

Meanwhile, in the U.S., more than 30 states require doctors to tell women their breast density.

‘I just want women to know’

Di Tomaso is encouraged by these small signs of change in Canada.

To her, it may begin with a simple line of text on a mammogram report, but it can make the difference between life or death.

“I just want women to know. I just didn’t want it to happen to anybody else,” she said.

(P.S.  I would like to add, what about the anxiety when you are diagnosed with breast cancer and you are told to wait for the surgery, as the cancer may be spreading???  I was told to “go biking” or “meditate” to “deal with the stress of waiting…” .  Nobody seems to worry about this…  Read the Wait Times article)

Written by Jonathan Ore. Produced by Jeff Goodes.

White Coat Black Art

Dense breasts and cancer detection


00:00 01:35

Cinda Lambert on discovering that her dense breasts made cancer detection difficult on mammograms 1:35

Dr. Paula Gordon, left, shows Cinda Lambert her mammogram and ultrasound results. (Brian Goldman/CBC)

%d bloggers like this:
search previous next tag category expand menu location phone mail time cart zoom edit close