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JAMA Oncology Patient Page
July 30, 2020

Benign vs Malignant Tumors

Author Affiliations
  • 1London North West University Healthcare NHS Trust, London, United Kingdom
JAMA Oncol. 2020;6(9):1488. doi:10.1001/jamaoncol.2020.2592

What Is a Tumor?

A tumor (also called neoplasm) is an abnormal mass of cells in the body. It is caused by cells dividing more than normal or not dying when they should. Tumors can be classified as benign or malignant.

Benign Tumors

Benign tumors are those that stay in their primary location without invading other sites of the body. They do not spread to local structures or to distant parts of the body. Benign tumors tend to grow slowly and have distinct borders.

Benign tumors are not usually problematic. However, they can become large and compress structures nearby, causing pain or other medical complications. For example, a large benign lung tumor could compress the trachea (windpipe) and cause difficulty in breathing. This would warrant urgent surgical removal. Benign tumors are unlikely to recur once removed. Common examples of benign tumors are fibroids in the uterus and lipomas in the skin.

Specific types of benign tumors can turn into malignant tumors. These are monitored closely and may require surgical removal. For example, colon polyps (another name for an abnormal mass of cells) can become malignant and are therefore usually surgically removed.

Malignant Tumors

Malignant tumors have cells that grow uncontrollably and spread locally and/or to distant sites. Malignant tumors are cancerous (ie, they invade other sites). They spread to distant sites via the bloodstream or the lymphatic system. This spread is called metastasis. Metastasis can occur anywhere in the body and most commonly is found in the liver, lungs, brain, and bone.

Malignant tumors can spread rapidly and require treatment to avoid spread. If they are caught early, treatment is likely to be surgery with possible chemotherapy or radiotherapy. If the cancer has spread, the treatment is likely to be systemic, such as chemotherapy or immunotherapy.

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Section Editor: Howard (Jack) West, MD.
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Article Information

Published Online: July 30, 2020. doi:10.1001/jamaoncol.2020.2592

Conflict of Interest Disclosures: None reported.

2 Comments for this article
Third category "Overdiagnosed tumors"
Jennifer Marti, MD | Weill Cornell Medicine
Please consider adding a third category: overdiagnosed tumors. These look malignant under the microscope, but behave in a benign fashion (these indolent tumors do not cause a symptom or death during the patient's lifetime). Commonly seen in melanoma, thyroid cancer, prostate cancer, and can be seen in some lung and screen detected, small ER+ breast cancers and DCIS. (https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2626156)
A border zone between benign and malignant tumours
guy pelouze, MD, MSc | Centre Hospitalier de Perpignan France
This presentation is very useful and beautifully illustrated. In order to give a more precise and prudent approach to human tumours, it seems you should mention that the border between benignness and malignancy is a grey zone. One can be sure of benignness only after a full pathologic examination.