Malignancy (from Latin male 'badly', and -gnus 'born') is the tendency
of a medical condition to become progressively worse; the term is most
familiar as a characterization of cancer.
A malignant tumor contrasts with a non-cancerous benign tumor in that
a malignancy is not self-limited in its growth, is capable of invading into
adjacent tissues, and may be capable of spreading to distant tissues. A benign
tumor has none of those properties, but may be harmful to health. The term
benign in more general medical use characterises a condition or growth
that is not cancerous, i.e. does not spread to other parts of the body or
invade nearby tissue.