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Breast cancer is a shockingly common disease - as many as 13% of females may get it at some point in their lives. And there's a lot of confusing info out there about it, from hormones to BRCA genes to risks and treatments. So we're here to break it down and give you everything you need to know about it, from symptoms and risk factors to treatments and current research.

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Chances are, you know someone  who’s had breast cancer.

It’s been estimated that as many as 13% of people assigned female at birth will get  it at some point in their lives. Given that we're more than 50  percent of people on the planet, that's a lot of breast cancer.

Plus, you can get breast cancer  even if you’re not female. The good news is we’ve learned a lot  about the disease in recent years. So today we’re going to take a  look at what breast cancer is, how it’s diagnosed, and what we can do about it. [♪ INTRO] So to start with, breast  cancer isn’t just one thing.

Of course, a cancer is considered a breast cancer if it originates in the  breast, AKA mammary tissue. They’re most common in the milk ducts,  which are called ductal carcinomas, or the milk-producing lobules,  which are called lobular carcinomas. There are also cancers that  can occur in the breast that also happen elsewhere too.

For instance, there’s a cancer called angiosarcoma that affects your blood or lymph vessels. But when an angiosarcoma happens in breast tissue? You guessed it: it’s thought  of, still, as a breast cancer.

And even rarer than that, people  can even get breast cancer without it being in the breast at all. See, some people are born with  mammary tissue outside of the breast, which is known as supernumerary  or ectopic breast tissue. And that tissue can develop breast cancer,  just like the correctly-located kind.

A 2019 case study reported on  a 36-year-old female patient who had breast cancer in some ectopic  breast tissue in her left armpit, without any sign of tumors in her breasts. The armpit is the most common  place for ectopic breast cancer, but it can also grow in other places,  like your thighs or your groin. And these body parts aren’t included  in routine breast cancer examinations, for somewhat obvious reasons, so these cancers can end up not getting diagnosed  as early as other ones would.

Which brings us to the diagnosis process; how does someone find out they have breast cancer? The earliest symptoms of breast  cancer are usually small, if you can see them at all. They can look a lot of ways, but  here are the major red flags.

People should be on alert for  lumps in the breast or armpits, or a change to the size and feel of your breasts, or red, puckered or rough skin on the breasts, or a change in the position of the nipples, or your nipples leaking fluid  when they shouldn’t be - so not during pregnancy or breastfeeding. And as alarming as all that sounds  when I say them all out loud, in reality these symptoms can be pretty subtle. And that's why the National Breast  Cancer Foundation recommends self-examination on top of  these routine mammograms to spot those early signs as soon as possible.

If your doctor is worried  about any of these things, they may get an ultrasound of your  breast, or possibly even a mammogram, which is a type of X-ray specifically  designed to take images of breast tissue. And they do this by squishing the  breast tissue between two plates, to spread it out as much as possible. Which is about as fun as it sounds.

If your doctor sees something  concerning on that mammogram, then you’ll need a biopsy. And if that biopsy detects  cancer, then your doctor will work to see how far it’s spread,  AKA what stage the cancer is. To learn more about how cancer staging works, you can check out the video we made all about it.

And look, mammograms may not be fun, but they are really important  especially as you get older. A mammogram can detect some cancers  before you can even feel them, so getting one when your doctor  recommends it is always a good call. Most patients are told to start getting  regular mammograms quite later in life, but that can change depending on what  risk factors they happen to have.

And there are a lot of potential  risk factors for breast cancer, so here we’re just going to touch on a few. The one thing I want to emphasize is  that these are risk factors, not causes. There’s nothing that causes  anyone to get any kind of cancer, but there are certain things  that can increase your risk.

Being assigned female at birth is  the biggest one for breast cancer, because most breast cancers occur in  people who are anatomically female. But, people of any sex can get breast cancer. So no matter what, it’s important to  be aware of the signs and the symptoms, and if you’re concerned, to get checked.

You’re also more likely to get  breast cancer as you grow older, especially once you’re over 50. Other breast cancer red flags are  if you have a family history of it, if you started menstruating before the age of 12, or if you’re overweight after menopause. There are lots of other risk factors too.

But again, they’re risk  factors, not direct causes. So it’s still important to keep up with self-exams whether you’ve got all of  these or even none of them. So now that we know a bit more  about what breast cancers are, let’s take a look at how they grow.

Many breast cancers are regulated  by estrogen and progesterone, which are hormones that perform a  whole bunch of functions in our bodies. They’re good things, normally. But breast cancer cells can  have estrogen and progesterone receptors on their surfaces, and  when those hormones bind to them, it triggers those cancer  cells to grow out of control.

So the same hormones that  you need for all sorts of essential stuff just so happen to be  Miracle-Gro for breast cancer cells. Another key player in breast cancer  growth is increased levels of a protein called human epidermal growth  factor receptor 2, or HER2. Breast cancers are called hormone or  HER2-positive when they’re sensitive to any of the three things we just mentioned.

And fortunately for us, those  same receptors are basically a built-in cheat code for treatment  for those types of cancers. Doctors can use targeted treatments to  lower the levels of hormones in the body, blocking the hormone’s  receptors, and they can also use antibodies to neutralize the HER2 protein. No growth factor means no growth of the tumor.

But around 15-20% of breast cancers don’t have receptors for estrogen, progesterone, or HER2. And these are called triple  negative breast cancers. Triple negative breast  cancers are extra aggressive, and they’re the ones that are more  likely to spread into other organs.

And because the targeted treatments  used for hormone and HER2 positive cancers don’t work here, doctors have  to fall back on more conventional cancer therapies like surgery, chemotherapy,  and radiation, to get the job done. More on that in a minute. Researchers are working hard  to understand the mechanisms involved in triple negative breast cancers.

But there’s a lot of factors  that gum up the process there. One of these complex factors  is, of course, genetics. You may have heard of two genes involved  in breast cancer, BRCA1 and BRCA2.

These are commonly referred  to as “tumor suppressor genes” because they help repair damaged DNA. At least, they do when they’re working correctly. But when BRCA1 and 2 are mutated, they drastically increase  the risk of some cancers.

Like I mentioned at the start,  research shows that as many as 13% of all females may develop  breast cancer in their lifetime. But for people who’ve inherited a BRCA1 mutation, that rate goes up to between 55 to 72%,  and it’s between 45 and 69% for BRCA2. BRCA mutations also increase the  risk of developing ovarian cancer, pancreatic cancer, prostate cancer,  all for the people who have those.

And so these BRCA mutations  are like, quadruple-whammys. But the good news is that there’s a  particular class of drugs that have been found to effectively stop  the growth of cancer cells with BRCA1 or BRCA2 mutations specifically. Plus, BRCA mutations aren’t very  common in the general population.

Only around 1 in 450 people have them. There are also genetic tests to  detect if you have a BRCA mutation, so patients with a family history  of those cancers we mentioned? They can have screenings to  determine their individual risks.

But BRCA genes aren’t the only  cancer-associated mutations out there. There are a bunch of other genes associated  with increased risk of breast cancer, although we don’t have time to get  through all of them in this video. But there’s another way someone’s  genes can affect their risk of cancer, and it’s much harder to detect.

Epigenetic changes are molecular  changes that can alter gene activity, like increasing or decreasing it’s expression. And they do this without  changing the DNA sequence itself. It can be like using a highlighter  to emphasize some writing or, like a black marker to smudge it out.

One way to do this is to add an  organic compound called a methyl group to specific spots on your DNA, which  tell your cells not to read that section. New research has found that 20% of triple  negative breast cancer patients were negative for BRCA1 gene mutations, but  they did have that gene methylated, meaning that even someone who  tests negative for BRCA1 mutations can still end up with a BRCA-related  cancer, which is pretty frustrating! But as we learn more about  how breast cancers work, researchers are getting better at  making super-targeted treatments.

For example, one study looking at over  500,000 women diagnosed with invasive breast cancer in England found that  the risk of dying from breast cancer has decreased from 15% in the  1990s to around 5% from 2010-2015. And a lot of that is thanks  to more effective treatments. With cancers whose growth is driven  by hormones, one way to treat them is to use hormone therapy.

For instance, you can try  to block the body's ability to produce those hormones in the first place. One way to turn down the hormone  production is by targeting the ovaries, which are the main sources  of estrogen and progesterone. And the easiest way to stop ovaries  from making hormones is to remove them.

There’s also targeted radiation,  but with both of these treatments, the goal is to make the ovaries  just stop working all together. So there’s a pretty clear downside, especially if you are a person who  wanted to use your ovaries later on. Other hormone-based treatments try  to stop the effects of the hormones on just the cancer cells,  which is a lot less drastic.

But hormone manipulation won’t be the treatment for all the kinds of breast cancer out there. With those triple negative breast cancers, where hormones aren’t driving the cancer growth, the main treatment is usually  either surgery to remove the tumor, or a mastectomy to remove the whole breast. And then, of course, we have chemo.

Chemotherapy uses drugs to  target fast-growing cells, and it does this by disrupting the  processes that those cells use to divide. Chemo can come with some  pretty nasty side effects, like hair loss, and mouth sores, and infections. That’s because those chemotherapy  drugs disrupt all of the fast-growing cells they find, whether they’re  cancer or just your body’s normal fast-growing cells, like hair and skin.

Which is why all those other, more  targeted treatments are appealing too. Still, if it’s a choice between  breast cancer and mouth sores, well. I know what I’m choosing.

There are a lot of other treatments out there, which we have thanks to decades of  research into this family of diseases. So even though it can seem grim,  there has never been a better time to be a person in treatment  for any kind of cancer. And as we learn more, we can  do more to detect and treat breast cancers more effectively,  which is good for all of us.

Thanks for watching this episode of SciShow. And an extra big thank you to  our patrons over on Patreon. Your support keeps these lights on and we couldn’t make videos like this without you.

We think you’re awesome. [♪ OUTRO]