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 do the terms benign and malignant mean?

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 do the terms "locally invasive" and "metastatic" mean?

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

  • Locally invasive—The tumor can invade the tissues surrounding it by sending out "fingers" of cancerous cells into the normal tissue.
  • Metastatic—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.

Clinical Trials

Clinical trials are research studies that evaluate a new medical approach, device, drug, or other treatment. As a Stanford Hospital & Clinics patient, you 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.

Before beginning treatment, ask your doctor about any clinical trials you should consider. Learn more about clinical trials for cancer patients.

Our Clinic

CANCER GENETICS PROGRAM

Expert care in a location convenient for you. Visit our clinic to make an appointment.

Call 650-498-6000 to make an appointment