Cancer may occur anywhere in the body. Therefore, doctors use a variety of technical names to distinguish among the many different types of cancer. In general, tumors are named according to the tissues from which they originate. There are 4 broad classifications of cancer:

Carcinomas arise in the epithelial tissue that covers all the external and internal body surfaces. Lung, breast, prostate, and colon cancers are the most frequent cancers of this type in the US. Adenocarcinomas are a subgroup of carcinomas where tumors arise in the epithelial tissue of a gland. Most kidney, prostate, and breast cancers are examples of adenocarcinomas. Other epithelial cancers are squamous cell cancers (often of the lung, oral cavity, or skin) and transitional carcinomas (of the lining of the bladder).

Sarcomas are cancers arising from cells found in the connective tissues of the body such as bone, cartilage, fat, and muscle. They often arise in bone or muscle, but may also arise in the connective tissue of an organ such as the breast, lung, kidney or uterus, which all more commonly produce carcinomas.

Hematologic cancers arise in the blood-forming cells of the bone marrow, and can be found in the blood or lymphatic system. There are 3 major types of hematologic cancers:

  • Leukemias are cancers of the immature blood cells that grow in the bone marrow and tend to accumulate in large numbers in the bloodstream. Leukemia is usually an overgrowth of white blood cells, but rarely may also involve the cells that produce red cells or platelets.
  • Lymphomas are cancers of the white blood cells that primarily occupy the lymph nodes and tissues of the body's immune system.
  • Multiple myelomas are cancers of the white blood cells (plasma cells) that produce the antibodies your body uses to fight infection. The name comes from the fact that these cancers tend to produce many (multiple) discrete tumors of these cells in bones and soft tissues (myelomas).

Cancers of the central nervous system (CNS) occur in either the brain or the spinal cord and are named according to the specific tissue type from which they arise. For example, tumors that arise from astrocytes (a small star-shaped cell) and glial cells (the cells that surround the nerves in the brain) are called astrocytomas and gliomas, respectively. Metastatic tumors from other sites can also occur in the brain as can lymphomas and involvement by leukemia.

Now that you have a better understanding of the biology and epidemiology of cancer, you may wish to lean more about how this disease is diagnosed and treated, what types of treatments are available, and what, if anything, you can do to reduce your risks for developing cancer. The answers to these and other questions may be found in Cancer Classroom 201.

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