First things first: What am I looking for?

When it comes to breast cancer screening, the first step is becoming familiar with what your normal is.

We have moved away from rigid “self breast exams” and more towards becoming “self-breast-aware”, simply meaning getting to know what is normal for you. Breasts naturally change throughout life - hormonal fluctuations, menstruation, pregnancy, breastfeeding, and menopause can all affect how they look and feel. The goal isn’t to scrutinize every little change or become fearful of your own body, but rather to recognize when something is new, unusual, or different for you.

Because, breast cancer doesn’t always present as the ‘lump’ people think it does.

While we often think about breast cancer as a new lump in the breast, in many cases people with a breast cancer diagnosis don’t feel a lump at all. Some breast cancers don’t form a distinct ‘lump’ either. There can also be other changes - some are subtle, and many can reflect benign breast conditions, but they can warrant ruling out something like breast cancer.

Here are some changes worth paying attention to:

Changes in breast shape or size: While breasts are never perfectly symmetrical, notice any new swelling, asymmetry, shape differences, or feeling of fullness on one side.
Skin changes: Dimpling, puckering, thickening, redness, or skin that resembles the texture of an orange peel (“peau d’orange”), and unexplained warmth or bruising.
Nipple changes: Shape changes, new inversion (a nipple turning inwards when normally not), or a new rash or scaling.
Nipple discharge: Particularly discharge that is bloody or happens when you aren’t breastfeeding.
A thickened or firm area
A lump or fullness in the armpit: The lymph nodes in the armpit are related to breast tissue, and can be swollen or larger when there is something going on in the breast.
Pain: While breast pain is much more commonly associated with non-cancerous conditions, new, persistent, or unexplained pain deserves further attention.

Most breast changes are not cancer; many of these symptoms are associated with non-cancerous breast conditions. But any new change or change that you are concerned about deserves more follow-up, and most importantly, you do not need to have a lump to warrant further investigation. Don’t wait for your next screening mammogram to have it assessed, because regularly scheduled imaging screening is intended for people without symptoms; a new symptom requires assessment, regardless of your age or when you last had a mammogram.

Breast density: An important piece to get familiar with

Your mammogram report can tell you more than whether something suspicious was seen - it can also tell you about your breast density, which is an important part of understanding both your breast cancer risk and the limitations of mammography.

What exactly is breast density?

Breasts contain a combination of fatty tissue and fibroglandular tissue, which includes the glands, ducts, and supporting connective tissue.

The term "Dense breasts" just means there is a higher proportion of fibroglandular tissue compared to fatty tissue in the breast. But it's not something you can feel yourself - it can only be determined with a mammogram. On a mammogram, the more dense fibroglandular tissue appears white while fatty tissue appears dark.

Breast density is classified into four categories:

Categories C and D are generally considered “dense breasts”. You will always find your breast density now on your mammogram report in Ontario.

Why does it matter?

Having dense breasts is more common than people think - about 40% of women aged 40-70 years of age have dense breasts. The proportion is higher among younger people, and breast density usually decreases with age.

Knowing your breast density is important for two key reasons:

Screening Difficulty: Many breast cancers appear white on a mammogram, but so does dense breast tissue. This makes mammograms much harder to read and therefore less sensitive as a screening tool because cancers can be more difficult to detect. This is why additional imaging like MRI or US may be recommended for women with dense breasts.
Cancer Risk: Breast density on its own is a risk factor for breast cancer. The more dense, the higher the risk. People with the most dense breasts (Category D) are thought to be 4-6 times more likely to get breast cancer than women with the least dense breasts (Category A).

Dense breasts are a normal variation in breast tissue. They are not a disease, and having them does not mean you will develop breast cancer.

However, it is important for people to know their breast density category so they can have informed discussions with their healthcare provider about whether additional screening is needed like an ultrasound or MRI, called supplementary screening. Many large organizations recommend supplemental screening for dense breasts due to the lowered sensitivity of a mammogram in these people, however it is not always available depending on province and hospital, and requires a healthcare provider’s referral. It is not part of the Ontario Breast Screening Program (OBSP) yet for those with dense breasts that are of average risk (not in the high-risk program). Organizations like Dense Breasts Canada are doing fantastic advocacy work in this area, and are a great resource to learn more about dense breasts.

The takeaway? A normal mammogram is reassuring, but it is not a guarantee that cancer is absent, particularly when breast density is high.

Knowing your density gives you another piece of information to use when making informed decisions about your screening and overall risk management.

Are mammograms safe?

Let’s talk about this, because it’s a question I get frequently.

Mammograms use low-dose X-rays to produce images of the breast. Many imaging modalities, including mammograms, expose the person to some ionizing radiation, and repeated exposure carries a small potential risk.

But let’s put this into context - the amount of ionizing radiation exposure from a mammogram is incredibly low, and small in the grand scheme of things when we consider that our annual background exposure to ionizing radiation is much, much greater (the amount we are exposed to just from day-to-day life). This picture (from densebreast-info.org) outlines this well.

For most people who are eligible for screening, the potential benefits of early detection far outweigh the radiation risk.

That doesn’t mean mammography is perfect, or that screening decisions should be made without considering the individual.

There are other potential harms to consider, including:

False-positive results: An abnormal finding may lead to additional imaging or a biopsy, even when cancer is not present.
False-negative results: A mammogram may miss a cancer, particularly in dense breasts.
Overdiagnosis: Screening can sometimes identify a cancer that would never have caused symptoms or become life-threatening during a person’s lifetime, potentially leading to treatment that would not otherwise have been needed.
Discomfort and anxiety: Compression during mammography can be uncomfortable, and waiting for results or undergoing follow-up tests can be incredibly stressful.

These are important considerations, and they are part of why screening decisions should be informed and individualized.

But please don’t let fear of radiation alone prevent you from having a conversation about screening. The goal is to understand the potential benefits and limitations, consider your individual risk, and make a decision that makes sense for you.

Are there alternatives to mammograms?

This is where we need to be careful about distinguishing between a different way of looking at breast tissue and a proven screening test.

Thermography: Is it an alternative?

Thermography uses an infrared camera to measure heat patterns at the surface of the body. Some providers market it as a radiation-free alternative to mammography.

The problem? It has not been established as a reliable replacement for mammography in breast cancer screening.

Thermography cannot reliably detect or rule out breast cancer, and Health Canada states that thermography equipment is not licensed for breast cancer screening in Canada.

Thermography is not considered an alternative screening method, and I do not recommend it - I've worked with many people who have felt it has given them good information, but a greater number of people who have had it miss frank, known breast cancers, which is of course incredibly harmful.

What about ultrasound and MRI?

Neither of these imaging techniques use ionizing radiation. However, they are not interchangeable with mammography, and are usually recommended as supplemental screening, meaning in addition to mammography.

Breast ultrasound and MRI can be useful in specific circumstances, particularly when breast tissue is dense or someone has a higher-than-average risk of breast cancer.

Both have their own limitations, including false-positive findings and the possibility of additional testing.

Breast cancer screening: When should you start?

Most large health organizations like the Canadian Cancer Society, the US Preventative Services Task Force, and the National Comprehensive Cancer Network recommend starting breast cancer screening with mammography at age 40 for those at average risk.

In Ontario, women are automatically invited into the Ontario Breast Screening Program (OBSP) between ages 50-74 for mammograms every two years. In October 2024, they expanded the program to include women aged 40-49 - these women now do not need a healthcare provider’s referral to get a mammogram. However these women are not automatically invited - you must call yourself to request screening, or, if you prefer, get your primary healthcare provider to send in a request. Every organization and program recommends something slightly different, which makes knowing what is best for you sometimes confusing. For example, for those at average risk, mammography every two years is recommended in Ontario, however other organizations like NCCN recommend annual screening mammograms. For those at high risk, Ontario does have a high-risk breast screening program, though, which recommends a mammogram with an ultrasound or MRI every year.

You can find more information or arrange an appointment through the Ontario Breast Screening Program.

How do I know if I am “high-risk”?

The Ontario Breast Screening Program considers someone high-risk if they fall under certain criteria.

Most of the qualifying criteria include family history, known positivity of high-risk genetic variants (like BRCA 1 or 2, PALB2, etc), or history of radiation to the chest. However, many people do not know their genetic status, and have no family history of breast cancer. In fact, it is estimated that up to 85% of people diagnosed with breast cancer have no family history of the disease.

So then how do you know if you might be at high-risk outside of these other factors?

By completing a validated breast cancer risk calculator.

There are a few available, but arguably the most comprehensive one is the Tyrer-Cuzick or IBIS, as it asks about the most risk factors, including breast density. In fact, the National Comprehensive Cancer Network (NCCN) recommends all women have a breast cancer risk assessment done by age 25, but many don't know this and aren't having this completed. If you are completing an online risk calculator for yourself, please be sure to bring the results to your healthcare provider who can help you interpret the results and discuss any limitations of the calculator, and help you to understand how it impacts you, and if there are other things to consider. Learn more about risk calculators here.

The limitations of mammogram screening: Detection is not prevention - how do I assess my risk factors?

This is the part of the conversation I think deserves much more attention.

Appropriate breast screening imaging is an important tool for detecting breast cancer earlier. But imaging does not prevent breast cancer from developing in the first place. And while we absolutely need effective screening programs, we also need to be having more conversations about risk assessment, modifiable risk factors, and the things we can do to support our long-term health.

Understanding your risk means looking beyond your mammogram, in part via breast cancer risk calculators, as above. Because breast cancer risk is multifactorial.

Some factors, such as age, inherited genetic mutations, family history, and certain reproductive or hormonal factors, are not things we can change. Other factors are potentially modifiable, like lifestyle - alcohol consumption, physical activity, healthy body weight (including building muscle!), fiber intake, & dietary patterns can also play a large role. Other factors that are gaining more data behind them are the gut microbiome, environmental exposures (ie endocrine disrupting chemicals, etc), and healthy sleep/wake cycles.

Your healthcare provider can help you understand some of the lifestyle-based risks, and the great thing about them is that they are modifiable, meaning we have agency over them and can make positive changes to reduce risk going forward.

So, where do we go from here?

Breast cancer awareness is about more than finding a lump.

It is about knowing what is normal for your body, understanding when a change needs assessment, knowing your breast density, making informed decisions about screening, and understanding the risk factors that may be relevant to you.

And it is also about prevention.

Not prevention in the sense that we can control every outcome — we can't. But prevention in the sense that we can take meaningful steps to support our health, understand our risks, and make informed choices about the things within our control.

A mammogram can be an important part of that picture. So can a conversation about family history, a more individualized screening plan, regular physical activity, a fiber-rich diet, and the many other foundations that support long-term health.

We need both early detection and prevention-focused healthcare.

Because the goal isn't simply to find cancer earlier. It's to support health more comprehensively, identify opportunities to reduce risk, and help people feel informed and empowered in their healthcare decisions.

A few practical next steps

If you take nothing else away from this article, start here:

Know your normal. Pay attention to new or persistent breast changes, and have them assessed promptly. You do not need to have a lump for something to warrant investigation.
Check your screening eligibility. In Ontario, eligible people aged 40–74 can access the OBSP, and those aged 40–49 can self-refer.
Find out your breast density. If you have had a mammogram, ask about your BI-RADS category and what it means for you.
Understand your personal risk. Discuss family history, genetics, and other relevant factors with your healthcare provider. Consider performing a breast cancer risk calculator on yourself with a trusted, validated online calculator, bringing the results to your healthcare provider to discuss.
Build supportive foundations. Focus on regular movement, a varied plant-forward diet, limiting alcohol, and sustainable sleep habits.

You don't need to do everything perfectly. You don't need to be afraid of every exposure or scrutinize every decision.

You simply need good information, a thoughtful plan, and healthcare that looks at the bigger picture.

And that is a much more empowering place to start.

This article is for general educational purposes only and is not intended to replace individualized medical advice, breast cancer screening recommendations, or diagnostic assessment. If you notice a new breast change, seek medical assessment promptly, even if your last mammogram was normal.