What is Cancer?

By Dr. Chitti Moorthy -Director, Departments of Radiation Medicine and Radiology,
New York Medical College, Valhalla , NY

The cause of cancer lies deep within the building blocks of a person's cells (genes and DNA). If these blocks become disorganized, cancer may develop.

Some forms of cancer may be inherited; they are passed down from parents to their children. For example, if a woman has close family members who have had breast cancer, she is more likely to get breast cancer.

Some cancers are caused by outside factors. For example, anyone who smokes is more likely to get lung throat or mouth cancer.

A tumor is a mass of abnormal cells. Tumors are either benign or malignant. Benign tumors usually grow very slowly and generally do not spread. Doctors can remove most of them. In the beginning, cancerous (malignant) tumors, usually stay in the organ where the cancer started. This is called localized disease. As cancers continue to grow, they are more likely to spread, or metastasize into the lymph nodes. This is called regional disease. When the cancer spreads beyond the nearby lymph nodes it is called distant disease. The more advanced the cancer (the more the cancer has spread) the more difficult it is to control or cure.

Doctors usually cannot tell if a tumor is cancer until a biopsy test is done. A tiny piece of tissue is removed with a needle or by surgery. A special doctor called a pathologist studies the tissue under a microscope to see if it is cancer. Often, more tests are done on the tissue if it is cancer. These tests let the doctor know more about the cancer. This information guides treatment. The pathologist might "grade" cancer from one to four. Grade one tumors have cells that look very similar to normal cells. Grade four tumors have cells that look very different from normal cells. Higher grade tumors are more likely to grow and spread.

Tumors also are "staged" to indicate the extent of the tumor. For example, tumors may be "called" stage one to stage four. The oncologist stagers a tumor based on the pathology report and other tests. Patients with the same stage and type of cancer have similar treatment in general, the higher the stage of cancer the more difficult it is to treat.

There are hundreds of different types of cancer. They are identified by the type of body tissue involved or by the body part involved. The major classifications of cancer are:

Carcinoma is a malignant tumor found in the outermost covering or lining of body surfaces or organs. These tumors are found on the skin, in the mouth and throat, stomach and bowel, or in organs like the breast, prostate, colon, lung or bladder.

Sarcoma is a malignant tumor found in connective tissues such as bone, muscle and cartilage.

Leukemia is a malignant disease found in bone marrow and other blood forming organs.

Glioma is cancer in the brain, spinal cord or nerves.

Lymphoma is a malignant tumor of the lymph glands or other lymphatic tissues.