Dictionary:

malignancy

  (mə-lĭg'nən-sē)

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1. also ma·lig·nance (-nəns) The state or quality of being malignant.
2. Pathology. A malignant tumor.

noun

A desire to harm others or to see others suffer: despitefulness, ill will, malevolence, malice, maliciousness, malignity, meanness, nastiness, poisonousness, spite, spitefulness, venomousness, viciousness. See attitude/good attitude/bad attitude/neutral attitude.

A tendency to progress in virulence. In popular usage, any condition that, if uncorrected, tends to worsen so as to cause serious illness or death. Cancer is the best known example.