What is the difference between benign and malignant?

A benign lump grows where it is and stays put. A malignant one can invade what is around it and travel elsewhere. Malignant is the word that means cancer.

A benign lump can still need treating if it presses on something or causes trouble. Benign does not always mean leave it alone, so ask what happens next either way.

Written by two physicians. Checked against patient information from the US National Cancer Institute and Cancer Research UK.