The malignant definition most people need comes from medicine: a malignant growth is cancerous, meaning its cells can invade nearby tissue and travel to distant organs. Outside the clinic, the same adjective describes a person, force or idea that is full of ill will and wants to cause harm.
Both uses share one feeling, that something bad is not staying put. Below you will find the malignant meaning in each setting, real sentences, the word family (malignancy, malign) and the clear line between malignant and benign that patients often ask about.
Entry at a glance
Meaning
Cancerous and able to spread; or deeply hostile and wishing harmPart of speech
AdjectivePronunciation
muh-LIG-nuhntWord forms
malignancy (noun), malignantly (adverb); related: malignOrigin
Late Latin malignare, to injure on purpose, from malignus, wicked; medical sense from the 1560sOpposite
Register
Formal and medical; literary when used of people
Malignant definition in two senses
- In medicine: a malignant tumour is a cancer. Its cells grow without the normal limits, push into surrounding tissue and can spread through the blood or lymph system to form new tumours elsewhere. Doctors also call some non cancer conditions malignant when they are severe and get worse fast, such as malignant hypertension, a sudden and dangerous rise in blood pressure.
- About people or forces: showing strong ill will or a wish to do harm. A malignant rumour is meant to damage someone; a malignant influence poisons a group from inside.
So when you define malignant, the key ideas are spreading and harmful. Something that is simply unpleasant or ugly is not malignant.
Malignant used in sentences
- The biopsy showed that the lump in her breast was not malignant, and the whole family relaxed.
- Surgeons removed the malignant growth and checked the nearby lymph nodes.
- He spoke about his rival with a malignant pleasure that made the room uncomfortable.
- Some historians describe the secret police of that era as a malignant presence in daily life.
- Untreated, a malignant melanoma can spread from the skin to other organs.
Malignant or benign?
Medicine treats benign and malignant as partners, using them to sort growths into two groups:
| Feature | Benign | Malignant |
|---|---|---|
| Counts as cancer | No | Yes |
| Growth | Usually slow, stays in one place | Often faster, invades nearby tissue |
| Spread | Does not spread to distant organs | Can spread (metastasize) |
| Edges | Usually smooth and clear | Often irregular |
A benign growth is not always harmless; one pressing on the brain may still need surgery. But it does not seed new tumours. Read the full page on benign for its everyday sense of kind and gentle.
Malignancy, malign and other forms
The noun malignancy can mean a cancer itself ("the scan found no malignancy") or the quality of being full of ill will. Malignantly is the rare adverb.
Watch the close relative malign. Used as a verb, malign means saying unfair, harmful things about someone: "She was maligned in the press for a decision she did not make." As an adjective it means evil in nature, close to the people sense of malignant. Pairings you will often see: malignant tumour, malignant cells, turned malignant, highly malignant, and in writing, a malignant force.
A Latin word for being born bad
English took malignant from French and from Late Latin malignantem, the present participle of malignare, to injure on purpose. Behind that sits Latin malignus, wicked or spiteful, built from male, badly, and a form linked to gignere, to give birth. The idea is something bad by its very nature.
Early church writers used it in the 1540s for a group they saw as wicked. The medical use, for a disease likely to kill, appears in the 1560s, and the sense of a person bent on causing suffering in the 1590s. The opposite, benign, comes from Latin for well born, so the pair mirror each other.
Where you will meet malignant
Most readers meet it in a hospital letter, a pathology report or a health news story. In fiction and essays it appears when a writer wants a stronger, colder word than evil, often for a villain, a regime or a creeping idea, much like insidious, which stresses hidden harm. In daily chat it is uncommon; people say cancerous or nasty instead.
For more terms from health and science, browse our science words hub.
Frequently asked questions
Does malignant always mean cancer?
In medicine a malignant tumour is a cancer. A few other conditions use the word to mean very severe and fast worsening, such as malignant hypertension. Outside medicine it means full of ill will, with no link to illness.
What is the opposite of malignant?
Benign is the direct opposite. Doctors call a harmless, non spreading growth benign, and in daily speech a benign smile or boss is mild and friendly.
Can a benign tumour become malignant?
A small number of harmless growths, such as certain colon polyps, may turn cancerous over the years, so these are often checked at intervals or taken out. Many never change. Only your doctor can say what applies to a particular growth.
Is malignant the same as malicious?
They are close when used of people, since both involve wanting to hurt. Malicious is the common everyday word for spiteful acts. Malignant sounds stronger and more formal and is mainly used in medicine.
How do you pronounce malignant?
Say muh-LIG-nuhnt. The g is sounded here, unlike in malign, where it is silent (muh-LINE).
What does malignancy mean?
Malignancy is the noun. It can mean a cancerous growth or the state of being cancerous, and less often the quality of being hateful.