Notice: Users may be experiencing issues with displaying some pages on stanfordhealthcare.org. We are working closely with our technical teams to resolve the issue as quickly as possible. Thank you for your patience.

Cancer

What Is Cancer?

Cancer is an abnormal growth of cells. Cancer cells rapidly reproduce despite restriction of space, nutrients shared by other cells, or signals sent from the body to stop reproduction. Cancer cells are often shaped differently from healthy cells, they do not function properly, and they can spread to many areas of the body. Tumors, abnormal growth of tissue, are clusters of cells that are capable of growing and dividing uncontrollably; their growth is not regulated.

Oncology is the study of cancer and tumors. The term "cancer" is used when a tumor is malignant, which is to say it has the potential to cause harm, including death.

What is the difference between benign and malignant cancer?

Tumors can be benign (noncancerous) or malignant (cancerous). Benign tumors tend to grow slowly and do not spread. Malignant tumors can grow rapidly, invade and destroy nearby normal tissues, and spread throughout the body.

What are "locally invasive cancer" and "metastatic cancer"?

Cancer is malignant because it can be "locally invasive" and "metastatic":

  • Locally invasive cancer—The tumor can invade the tissues surrounding it by sending out "fingers" of cancerous cells into the normal tissue.
  • Metastatic cancer—The tumor can send cells into other tissues in the body, which may be distant from the original tumor.

What are primary tumors?

The original tumor is called the "primary tumor." Its cells, which travel through the body, can begin the formation of new tumors in other organs. These new tumors are referred to as "secondary tumors."

The cancerous cells travel through the blood (circulatory system) or lymphatic system to form secondary tumors. The lymphatic system is a series of small vessels that collect waste from cells, carrying it into larger vessels, and finally into lymph nodes. Lymph fluid eventually drains into the bloodstream.

Condition Spotlight

Stanford Health Care Dietitian Discusses Organic Versus Conventional Foods Watch Video
Sugar and Health - the Sweet, the Sour, and the Sticky!
Sugar and Health - the Sweet, the Sour, and the Sticky! Play Video | 1:31:36
Lung Cancer Myths & Facts
Lung Cancer Myths & Facts Read Story
Cancer Survivorship: A Role for Integrative Medicine Watch Video
Stanford Cancer Center: Innovations In Cancer Care
Stanford Cancer Center: Innovations In Cancer Care Play Video | 4:43
I Can't Do It All: Getting Help in Caring for Your Loved One
I Can't Do It All: Getting Help in Caring for Your Loved One Play Video | 1:19:51
Stanford's Dermato-Oncology Clinic Featured on NBC Bay Area Watch Video
Sexuality: Retaining and Rediscovering Intimacy
Sexuality: Retaining and Rediscovering Intimacy Play Video | 1:17:18
Cancer in the Family
Cancer in the Family Play Video | 1:25:22

Clinical Trials for Cancer

Clinical trials are research studies that evaluate a new medical approach, device, drug, or other treatment. As a Stanford Health Care patient, you may have access to the latest, advanced clinical trials.

Open trials refer to studies currently accepting participants. Closed trials are not currently enrolling, but may open in the future.

Open Trials Closed Trials
Clinical Trials View All »

Other Clinics