What are the differences between cancer and tumour? I mean is it in the DNA or shape or something else... And how can a benign tumour turn into a malignant tumour? The body has a lot of tumours all the time, however not all of them become cancerous, why is this so?

So my main question is: What is so special about cancer cells that they can get out of control unlike an ordinary benign tumour?

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    $\begingroup$ please accept an answer. It is considered impolite when the question has been answered to the fullest and the OP (original poster) has not accepted an answer. It means that the OP is expecting something more. So if you feel that the question has been answered, then please accept the answer which has suited you. $\endgroup$
    – One Face
    Commented Jan 29, 2015 at 14:01
  • $\begingroup$ What is the difference between "a car" and a "Volvo XC60"? What is difference between "disease" and "sarcoidosis"? What is the difference between "planet" and "Earth"? $\endgroup$
    – Ilan
    Commented Aug 8, 2015 at 6:16

2 Answers 2


A tumour is simply a space-occupying lesion (something that should not be there, that is; a "lump") caused by abnormal cell replication.

(In medicine, the word "tumour" literally means "swelling", and can sometimes refer to that instead, but that's a different story).

Cancer is a disease in which cell replication is totally out of control. What causes cancer is damage to the genes (DNA) which normally stop cell replication when it needs to be stopped.

There's no such thing as an "ordinary tumour"; all tumours are abnormal. However, what makes a benign (harmless) tumour different from a cancerous tumour is that there is still some mechanisms stopping the cells inside the tumour from replicating; they are doing it more than they should, but they are not totally out of control. When those last mechanisms are broken too, the tumour is cancerous.

(This is a simplified explanation; the actual explanation is a semester-long university course. It's mostly accurate for the layman, though)

  • $\begingroup$ Thanks! and where can I get the "actual explanation"? can you give me an outer source for that?(book/site etc) $\endgroup$ Commented Jan 24, 2015 at 17:45
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    $\begingroup$ Wikipedia is always a good start; the article on cancer has a "Further Reading" section down near the bottom. $\endgroup$ Commented Jan 24, 2015 at 17:49
  • $\begingroup$ Uterine smooth muscle tumors other than the ordinary leiomyomas and leiomyosarcomas: a review of selected variants with emphasis on recent advances and unusual morphology that may cause concern for malignancy. ') Just nit picking here, but I do believe many kinds of "tumors" are so common that they deserve the appellation "ordinary". Subcutaneous lipomas, for instance. $\endgroup$ Commented Jan 24, 2015 at 21:22
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    $\begingroup$ Hallmarks of Cancer: The Next Generation is a review article that'll provide a great understanding, sorry for no link, on my phone. $\endgroup$
    – CKM
    Commented Jan 24, 2015 at 22:44
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    $\begingroup$ @Kendall here is the link to the 2011 Cell article by the same name. I could download the PDF at home, so I believe it's open-access. $\endgroup$
    – MattDMo
    Commented Jan 24, 2015 at 23:36

Tl;dr answer, tumors are abnormal growth (or swelling, thanks to Malic for pointing out) of any kind. The kinds of tumors are benign and malignant.

Benign tumors are usually slow growing and harmless. Example would be a lipoma.

Malignant tumors are otherwise called cancers. They generally have a bad prognosis. Very few cancers are curable.

Swelling over an injury (which is also called tumor) is due to local transudation (shift of plasma from capillaries). This is temporary and usually goes down one the injury heals.

  • $\begingroup$ All of the tumors are abnormal? I heard that if part of the body get hurt, the body does a tumor on purpose to fix the part that get hurt, is it true? and there is a lot of small tumors in the body at a given moment? $\endgroup$ Commented Jan 25, 2015 at 9:32
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    $\begingroup$ When a part of body swells, it is also called tumor. Thanks for pointing out! @MalicOfSdom. But that swelling is also considered pathological. As it is a deviation from physiology $\endgroup$
    – One Face
    Commented Jan 25, 2015 at 9:35
  • $\begingroup$ haa! so every time a part of the body swells it is tumor...scary! and does a benign tumor can turn to a malignant tumor? $\endgroup$ Commented Jan 25, 2015 at 9:42
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    $\begingroup$ @CRags - no, I don't agree; if I did, I would not have left that comment. I define "cure" like any normal person: it's gone and will never bother you again. It is possible, and it is done every day, to declare a cancer patient cured. Childhood leukemia is now a largely curable disease; others include some lymphomas, cervical cancer, and others if caught early. Clearly there are some that, regardless the initial response, can still come back. I'm just saying, don't make claims which are untrue. BCC is a malignant cancer with a very good prognosis, if not even excellent. $\endgroup$ Commented Jan 29, 2015 at 16:20
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    $\begingroup$ Yes, I got it. I will be more careful @anongoodnurse Thanks for helping me answer better $\endgroup$
    – One Face
    Commented Jan 29, 2015 at 16:33

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