What are benign and malignant tumors?


A tumor is a lump of damaged cells. A malignant tumor is cancerous. Malignant tumors cause trouble to cells around them. They can also spread to other parts of the body, causing trouble there too.

Dr. Ajay K. Sahajpal, MD
Transplant Surgeon

Tumors are masses created by abnormal cell growth. Benign tumors tend to grow, but do not invade beyond its borders and do not metastasize. Malignant tumors tend to be invasive and can metastasize. A malignant tumor is by definition a cancer.

A benign tumor is a collection of cells which demonstrate no transformation into a disease-causing structure. A malignant tumor is one that contains cells which are rapidly transforming and tends to affect its surrounding structures. Some malignant tumors may be slow growing in nature, but most tend to be relatively fast growing when compared to benign tumors. Malignant tumors most likely require some form of treatment with either chemotherapy, radiation or surgery. Benign tumors (for example, meningiomas) tend to be watched over time.

No matter where they are located in the body, tumors are classified as benign or malignant.

Benign tumors are slow-growing, non-cancerous cell masses that have a defined edge and do not spread to other parts of the body. The cells in a tumor are similar to normal cells. Often, these tumors can be removed surgically and usually do not recur.

Malignant, or cancerous, tumors have cells that look different from normal cells. They can quickly invade the surrounding tissue and often have edges that are hard to define, which makes it difficult to remove the entire tumor surgically.

This answer is based on source information from the National Institute of Neurological Disorders and Stroke. The contents of this website are for informational purposes only and are not intended to be a substitute for professional medical advice, diagnosis, or treatment. Nor does the contents of this website constitute the establishment of a physician patient or therapeutic relationship. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.