According to data provided by the National Cancer Institute, more than 1.5 million new cases of cancer are diagnosed in the United States each year, and more than half a million people die from cancer. Although some types of cancers are more common--those that arise from the breast, lung and colon, for example--there are an enormous number of different kinds of cancer that can arise from almost anywhere in the body.
Tumors
Not all cancers are tumors, and not all tumors are cancers. A tumor is simply a growth of cells that make a mass. Tumors can be benign, and do little to harm the patient, or they can be malignant. A malignant tumor is called a cancer. Some cancers may not make a tumor or mass: cancers of the blood, for example.
Cancers
The term "cancer" is a Latin word that means, literally, "crab." This is a very accurate description of cancer. Cancer occurs when a group of abnormal cells in the body begins to grow uncontrollably and invade the normal tissue. When the cancer invades the surrounding tissue, it makes a pattern like a crab with long legs.
Types of Cancer
Most cancers can be divided up into categories.
Cancer can be classified by where it originated. Breast carcinomas originate in the breast. Even if the breast cancer spreads to the brain, it is still considered breast cancer, rather than brain cancer.
Cancers are also categorized by what kinds of cells from which they arise. The four main categories are carcinomas, sarcomas, leukemias and lymphomas.
Carcinomas arise from cells that line the inside of organs, from the skin or from glands within organs. A breast carcinoma, for example, is a cancer that arises from the milk-producing glands--the ducts--within the breast. A colon carcinoma is a cancer that arises from the lining of the large intestine.
Sarcomas arise from cells that make up the body's connective tissue, muscles, bones, fat and nerves. Osteosarcoma, for example, is a cancer of the bone.
Leukemias and lymphomas are cancers of the blood cells. Leukemias are cancers of the cells in the bone marrow that produce the blood cells that circulate in the blood. Lymphomas are cancers of white blood cells called lymphocytes, which are within the lymph nodes throughout the body.
All of these types of cancers can be further divided into subtypes. Some cancers, such as some types of leukemias, may be classified very specifically--according to which sequence of DNA in the cancer cells are abnormal.
Importance of Classifying Cancers
Knowing the type of cancer is very important. Different types of cancer can behave very differently and need different types of treatments. Some types of cancers are able to be removed with surgery; other types of cancers may not.
The more specifically a doctor can classify a tumor, the better he will be able to "target" his therapy--to kill only the cancer cells in the body, and not damage healthy tissue. This can avoid many of the side effects of the treatment. For example, some subtypes of breast cancer can be treated with medications that target certain proteins on the cancer cells; this medication is much less toxic than other chemotherapy drugs, which can kill normal cells in the body.
Conclusion
Although the number of different kinds of cancer can be overwhelming, it is possible to categorize most of them.Classifying cancer is important for both doctor and patient: Knowing what kind of cancer is present will give a better understanding of how it will behave, and how it can be treated. As medical technology continues to improve, it may be possible to very specifically classify a cancer; this may enable researchers to develop drugs that will safely and effectively destroy cancer cells in the body.
References
- Merriam-Webster Dictionary: Cancer Definition
- American Cancer Society: What is Cancer
- National Cancer Institute: Cancer Statistics Review 1975-2007: Estimated New Cancer Cases and Deaths for 2010
- Cancer.net: What is Cancer
- Merriam-Webster Dictionary: Osteosarcoma Definition
- National Cancer Institute: "Tamoxifen: Questions and Answers"
