These ferocious fighters are too small for us to see without a microscope, but they are capable of overtaking just about any organ in your body.

這些兇猛的細胞非常小，我們要用顯微鏡才看得見，不過他們可是有能力侵蝕你身體裡的任一個器官。

They are cancer cells, and they're actually constantly arising inside of us.

他們是癌細胞，而實際上他們正持續地在我們的身體裡增生。

Most of the time, our immune system seeks them out and neutralizes them, but it's not always successful.

大多時候，我們的免疫系統會找出並消滅他們，不過也不是每次都能成功。

That's because cancer is not simply one disease; it's many.

因為癌症不是一種單一的疾病，而是很多。

Cancer cells can attack your brain, your liver, your lungs, and a lot of other super-important parts of your body.

癌細胞可以攻擊你的大腦、肝、肺，以及其他很多重要的部位。

But what about your heart? Heart cancer isn't a thing you hear much about.

但你的心臟呢？你很少聽到「心癌」對吧？

That's because it almost doesn't exist.

這是因為心臟的癌症幾乎不存在。

Most hospitals report fewer than one case of heart cancer per year.

絕大多數的醫院一年大概只有不到一起的心臟癌症病例。

So, why are tumors on this organ so rare?

所以，為什麼心臟上不容易長腫瘤呢？

Well, those cancer cells we're just talking about get their power from their ability to divide and multiply.

這麼說吧，癌細胞之所以強大是因為他分裂增生的能力。

Cancer cells become a problem when they start to divide uncontrollably and takeover everything.

癌細胞最大的問題是他會不受控制地分裂並掌控一切。

When they're behaving normally, cells know when to stop replicating based on instructions encoded in their DNA.

在正常情況下，細胞們會依據 DNA 的指示，知道何時該停止分裂。

Cancer cells just don't get the memo and keep replicating, and then replicating, and then replicating some more

癌細胞卻不照指示，不停地分裂、分裂、再分裂。

But unlike cells in other organs, our heart cells do almost all of their dividing during fetal development.

但心臟細胞和其他器官不同，幾乎在胚胎發育的過程中就同時完成了分裂。

Sometimes, but not often, tumors can form in fetuses while these cells are still able to divide.

有時，但不常，在心細胞還在分裂的時候，腫瘤會在胚胎時期形成，

Once we're born, though, our heart cells stop dividing.

一旦我們出生了，我們的心臟細胞就停止分裂了。

Tumors that might have grown while we were in utero tend to stop growing at this point.

在我們還待在子宮裡時，長大的腫瘤也在我們出生的這一刻停止了成長。

That's because our heart are made mostly of muscle cells, which can grow in proportion to our bodies, but they don't multiply the same way that other cells in our body do.

而這是因為心臟幾乎都是由肌肉細胞組成，會和我們的身體成比例成長，但不像其他細胞一樣地分裂。

See, every cells in your body has a chance of becoming abnormal if its DNA is damaged.

每一個細胞都有機會因為 DNA 的損傷而變得不正常。

A few abnormal cells is OK, so long as they are kept under control by our immune system.

如果只有一點點是沒問題的，我們的免疫系統會控制住情況。

The problem arises when these cells start to divide uncontrollably, and form lumps of growth.

但當這些細胞開始無止盡分裂，形成腫塊時，問題就來了。

Some of these growths might be benign, but sometimes they aren't.

有時這些腫瘤是良性的，不過有時並不是。

But since very little cell division happens in the heart, problem cells are much less likely to turn into a cancerous growth.

因為心臟細胞很少分裂，因此有問題的細胞很少有機會能分裂成一整個癌症腫瘤。

So, yes, you can get heart cancer. But it's extremely rare, and either begins elsewhere in the body and spreads to the heart through the bloodstream,

沒錯，你可能得到心癌，但機率很小，更有可能是從別處發病，然後順著血流到達心臟，

or it affects babies who got the disease in the utero.

又或是當嬰兒還在子宮內時就已經得病。

Which means: if you're old enough to be watching this video, you probably have one less thing to worry about.

也就是說，如果你還能活著看到(並看懂)這部影片，那你可以少擔心一件事了(得到心癌)

Thanks for asking, and thanks especially to all of our patrons on Patreon who keep these answers coming.

謝謝你們的問題，也謝謝在 Patreon 上的贊助者們，有了你們，我們才有源源不絕的問題可以解答。

If you'd like to submit questions to be answered, or get this Quick Questions a few days before everyone else,

如果你想問問題，或是想比別人更早一點看到這些 Quick Question 影片，

go to Patreon.com/scishow. And don't forget to go to Youtube.com/scishow and subscribe!

可以上 Patreon 的網站找找。也別忘了到 Youtube 去訂閱喔！