What is the difference between benign and malignant tumors?

The main difference is whether the tumor can spread. A tumor is a lump of tissue that forms when cells grow and multiply when they shouldn't. Tumors can be cancerous or not cancerous (benign).

Malignant tumors are cancerous. According to the National Cancer Institute, cancerous tumors spread into, or invade, nearby tissues, and they can travel to distant places in the body to form new tumors, a process called metastasis.

Benign tumors do not spread into or invade nearby tissues. When removed, benign tumors usually don't grow back, whereas cancerous tumors sometimes do.

It is worth noting that benign does not always mean harmless. Benign tumors can sometimes be quite large, and some can cause serious symptoms or even be life threatening, such as benign tumors in the brain.

Only a healthcare team can determine whether a specific tumor is benign or malignant, usually with a biopsy and other tests. If you have questions about a tumor, your doctor can explain what it means for your situation.