What is cancer?

Cancer is a disease of cells. It is an abnormal growth of cells which tend to proliferate in an uncontrolled way and, in some cases, to metastasize (spread).

Cancer is also called malignancy. A cancerous growth or tumor is sometimes referred to as a malignant growth or tumor. A non-malignant growth or tumor is referred to as benign. Benign tumors are not cancer.

Cancer is not one disease. It is a group of more than 100 different and distinctive diseases. Cancer is NOT contagious.

Cancer can involve any tissue of the body and have many different forms in each body area. Most cancers are named for the type of cell or organ in which they start. If a cancer spreads (metastasizes), the new tumor bears the same name as the original (primary) tumor.

Cancer is the Latin word for crab. The ancients used the word to mean a malignancy, doubtless because of the crab-like tenacity a malignant tumor sometimes seems to show in grasping the tissues it invades. Cancer may also be called malignancy, a malignant tumor, or a neoplasm (literally, a new growth).

What are the most common types of cancer?

The frequency of a particular cancer may depend on gender.

The list of common cancers includes cancers that are diagnosed with the greatest frequency in the United States. Cancer incidence statistics from the American Cancer Society and other resources were used to create the list. To qualify as a common cancer, the estimated annual incidence for 2006 had to be 30,000 cases or more.

The most common type of cancer on the list is non-melanoma skin cancer, with more than 1,000,000 new cases expected in the United States in 2006. Non-melanoma skin cancers represent about half of all cancers diagnosed in the US.

The cancer on the list with the lowest incidence is thyroid cancer. The estimated number of new cases of thyroid cancer for 2006 is 30,180.

Because colon and rectal cancers are often referred to as "colorectal cancers," these two cancer types were combined for the list. For 2006, the estimated number of new cases of colon cancer is 106,680, and the estimated number of new cases of rectal cancer is 41,930. These numbers are slightly larger than those estimated for 2005.

Kidney cancer can be divided into two major groups, renal parenchyma cancers and renal pelvis cancers. Approximately 82 percent of kidney cancers develop in the renal parenchyma,2 and nearly all of these cancers are renal cell cancers. The estimated number of new cases of renal cell cancer for 2006 is 31,890.

Leukemia as a cancer type includes acute lymphoblastic (or lymphoid) leukemia, chronic lymphocytic leukemia, acute myeloid leukemia, chronic myelogenous (or myeloid) leukemia, and other forms of leukemia. It is estimated that more than 35,000 new cases of leukemia will be diagnosed in the United States in 2006, with acute myeloid leukemia being the most common type (approximately 12,000 new cases). The total number of new leukemia cases estimated for 2006 is slightly larger than the number estimated for 2005.