It's estimated that more than 11 million people in the United States have some form of cancer. There are more than 200 different types of cancer, although many are quite rare. The following are the 10 most commonly diagnosed cancer types in 2009 and the estimated number of cancer patients affected by each:

  1. Non-melanoma skin cancer. Affecting more than 1 million people a year, skin cancer can form in the skin cells on any part of the body, though most commonly on skin that’s been exposed to the sun. There are several types of skin cancers, including squamous cell skin cancer, found in the flat cells on the top of the skin, and basal cell skin cancer, found in the round cells deeper inside skin's outer layer. Most commonly, skin cancer affects older people or people who have a compromised immune system.
  2. Lung cancer. Roughly 219,440 cases of this deadly cancer were diagnosed in 2009. Lung cancer strikes the cells inside the lining of the lungs. There are two primary types of lung cancer — small cell and non-small cell lung cancer. Lung cancer claims nearly 160,000 lives annually.
  3. Breast cancer. This type of cancer will affect 194,280 people in 2009. This is by far the most common cancer in women, says Len Lichtenfeld, MD, deputy chief medical officer for the American Cancer Society. While the overwhelming majority of breast cancer patients are women, about 1,900 cases are diagnosed in men each year.
  4. Prostate cancer. Just over 192,200 cases of prostate cancer are diagnosed annually. Dr. Lichtenfeld says that this is the most common cancer to affect men, most often men over age 50. The prostate gland is a part of the reproductive system in men and is found at the base of the bladder, near the rectum. This type of cancer develops in the tissues inside the prostate gland.
  5. Colorectal cancer. There will be about 146,970 new cases of colon and rectal cancers combined in 2010. The colon is part of the large intestine, which helps to break down and digest food, and the rectum is the end of the large intestine that is nearest the anus.
  6. Bladder cancer. Nearly 71,000 people will receive this diagnosis in 2010. The bladder can be affected by cancer cells that develop within its tissues. The most common type is transitional cell carcinoma, but others, such as adenocarcinomas and squamous cell carcinomas, may also occur, depending on which bladder cells are involved.
  7. Melanoma. Predicted to strike close to 68,720 people, melanoma is another type of skin cancer. It forms in the skin's melanocyte cells, which produce the brown pigment melanin. Because melanoma occurs in skin that contains a lot of pigment, it frequently begins in moles. Melanoma may also be found in other pigmented parts of the body, like the intestines or even the eyes.
  8. Non-Hodgkin lymphoma. Affecting 65,980 people, this is the term for a number of different but related cancers involving white blood cells, or lymphocytes. This type of cancer is frequently characterized by swollen lymph nodes, fevers, and weight loss. People of any age can develop non-Hodgkin lymphoma. There are many different types of non-Hodgkin lymphoma that affect different cells and parts of the body, with varying prognoses and treatment.
  9. Kidney cancer. Kidney cancer is diagnosed in more than 49,000 people each year. The kidneys are the organs that help to excrete waste from the body in the form of urine. Cancer can form inside the tissues or ducts of the kidneys. Although kidney cancer develops mainly in people over 40, one type of kidney tumor usually affects young children.
  10. Leukemia. Approximately 44,790 cases of leukemia were predicted for 2009. The four main types of leukemia are acute myeloid leukemia, acute lymphocytic leukemia, chronic lymphocytic leukemia, and chronic myeloid leukemia. These types of cancer often form inside the bone marrow or other cells and tissues that form blood cells, and are known as blood cancers. Leukemia results in overproduction of certain kinds of white blood cells, which then circulate in the bloodstream. Leukemia can be chronic — a slow-growing type of cancer that begins without symptoms — or acute, meaning the cells can't function normally and symptoms progress rapidly. It affects both adults and children, and kills more children under age 20 than any other cancer.

Other types of cancer that are important to mention include pancreatic, endometrial (uterine), thyroid, and sarcomas, each of which affects fewer than 43,000 people annually.