Somerville. in some connections, malignity seems rather more pertinently applied to a radical depravity of nature, and malignancy to indications of this depravity, in temper and conduct in particular instances.

Webster's Revised Unabridged Dictionary (1913)

Example sentences

cancer Doctors suspect smoking has lot to do with cancer.

Popularity over time

Word	1850 → 2019	Trend
malignancy		rising
malignity		steady
malignance		steady
cancer		rising
poisonousness		steady
virulency		steady

Use in printed books, per decade from 1850 to 2019.

By length

6 letters: cancer², malice²
9 letters: virulence³, malignity, virulency
10 letters: malignance
13 letters: poisonousness

The small number after each word is its number of syllables (cancer² = 2 syllables).