Benign Tumors vs. Malignant Tumors

Mesothelioma
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Facts About Benign and Malignant Tumors

The term "benign" refers to a tumor, condition, or growth that is not cancerous. This means it is localized and has not spread (aka metastasize) to other parts of the body or invaded and destroyed nearby tissue.
In general, a benign tumor or condition is usually not harmful and benign tumors usually grow slowly. They can usually be removed and in most cases they never come back. However, if a benign tumor is big enough, the size and weight can press on nearby organs, blood vessels, and nerves and thus cause problems.

The opposite of benign is malignant tumor. Malignant tumors are cancer, where the cancer cells can invade and damage tissues and organs near the tumor. Also, cancer cells can break away from a malignant tumor and enter the lymphatic system or the bloodstream. This is how cancer spreads from the original tumor to form new tumors in other parts of the body (aka metastasize).

However, although benign tumors are mostly harmless, they cause more than 13,000 annual deaths in the USA, which can be compared to more than 500,000 annual deaths from cancer (malignant tumors).

A type of benign tumor that used to be called "benign fibrous mesothelioma" can form around the lungs in the pleura. This type of tumor starts in the tissues under the mesothelium and is not a type of mesothelioma. This is typically not cancerous, but can later progress to it.

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