Cancer is the catchall term applied to diseases caused by the uncontrolled growth of abnormal cells. Cancer isn't one disease. It is many different diseases, more than 100 and counting.
Each kind of cancer is usually named for the cell type in which it begins — cancer that starts in a lung is called lung cancer; cancer that starts in pigment cells in the skin, which are known as melanocytes, is called melanoma.
When detected and treated early, cancer can often be stopped. That said, cancer is a leading cause of death and disability around the world.
Ask the doctor: Should I be screened for lung cancer?
The major factors that determine a man's risk for prostate cancer are age, family history, and race and ethnicity. It is not proven that men at higher risk who are tested for hidden cancer are less likely to develop more advanced cancer or die from it.
Basal cell carcinoma, also called epithelioma, is the uncontrolled growth of the skin's basal cells. These are the cells that line the deepest layer of the epidermis, the skin's outermost layer. This type of cancer rarely spreads to other parts of the body.
It is mainly caused by repeated long-term exposure to sunlight. Light-skinned people who spent a lot of time in the sun as children, or who spend time in tanning booths, are especially susceptible. X-ray treatments for acne and exposure to industrial pollutants such as arsenic and hydrocarbons also increase the risk of developing basal cell carcinoma.
Basal cell carcinoma is the most common skin cancer in the United States, with nearly 3 million cases diagnosed each year.
Squamous cell carcinoma is a life-threatening type of skin cancer. Squamous cells are small, flat cells in the outer layer of skin. When these cells become cancerous, they typically develop into rounded skin tumors that can be flat or raised. Sometimes the skin around the tumor gets red and swollen. Squamous cell carcinoma can also occur on the penis or vulva.
Squamous cell carcinoma sometimes develops from a precancerous skin growth called an actinic keratosis. The risk of developing this type of skin cancer is increased among fair-skinned and fair-haired people who have repeatedly been exposed to strong sunlight, individuals who had freckles as a child, and those with blue eyes. Other risk factors include taking immunosuppressants (drugs that weaken the immune system) and being exposed to industrial pollutants such as arsenic, tar, and industrial oils.
Having had genital warts in the past is a major risk factor for genital squamous cell carcinoma.
Melanoma is the deadliest form of skin cancer. It occurs when pigment-making cells in the skin, called melanocytes, begin to reproduce uncontrollably. Melanoma can form from an existing mole or develop on unblemished skin.
The most common type of melanoma spreads on the skin's surface. It is called superficial spreading melanoma. It may stay on the surface or grow down into deeper tissues. Other types of melanoma can start anywhere on or inside the body, including under fingernails or toenails and inside the eye.
Melanoma rarely occurs before age 18. However, the risk of melanoma rises rapidly in young adulthood, making it one of the most common life-threatening forms of cancer in people between the ages of 20 and 50. After age 50, the risk of melanoma rises more slowly with advancing age.
Multiple myeloma is a kind of bone marrow cancer. It is caused by the uncontrolled growth of a type of white blood cell known as plasma cells. Plasma cells make antibodies called immunoglobulins to fight infections.
In multiple myeloma, cancerous plasma cells multiply rapidly in the bone marrow. They eventually invade the outer layers of the bones. This can weaken bones so much that even a small injury can cause a bone to break.
The cancerous plasma cells also make a lot of immunoglobulins. This can cause the blood to become thick and sticky, and lead to the formation of blood clots. At the same time, blood levels of other antibodies drop, leaving the person open to infections.
Kaposi's sarcoma is a type of cancer caused by the human herpes virus 8. It appears as red or purple patches on the skin, mouth, lungs, liver, or digestive system.
Kaposi's sarcoma was a rare and relatively harmless disease until the AIDS epidemic began. An aggressive form of the disease, AIDS-related Kaposi's sarcoma, occurs in people with severely weakened immune systems. It is now the most common type of Kaposi's sarcoma.
There are four main types of Kaposi's sarcoma:
Leukemia is a type of cancer that harms the body's ability to make healthy blood cells. It starts in the bone marrow, the soft center of various bones. This is where new blood cells are made. There are three main types of blood cells:
Leukemia usually refers to cancer of the white blood cells. It tends to affect one of the two major types of white blood cells: lymphocytes and granulocytes. These cells circulate through the bloodstream and the lymph system to help the body fight off viruses, infections, and other invading organisms. Leukemia arising from cancerous lymphocytes is called lymphocytic leukemia; leukemia from cancerous granulocytes is called myeloid or myelogenous leukemia.
Leukemia is either acute (comes on suddenly) or chronic (lasts a long time). Acute leukemia affects adults and children. Chronic leukemia rarely affects children.
Lymphoma is a cancer of the lymph system (also called the lymphatic system). The lymph system is a network of tissue, vessels, and fluid (called lymph) that runs through all parts of the body. As part of the immune system, it helps protect the body from infection and disease by collecting and destroying invading organisms, such as bacteria, viruses, abnormal cells.
The lymph system includes:
Lymph: a clear fluid that carries white blood cells through the lymph system. White blood cells help fight infection.
Abnormal cells seen on a Pap smear range from mild to severe, and do not necessarily mean that you have cervical cancer.
Atypical cells, the mildest kind of abnormality, are often caused by simple infections or inflammation. Sometimes they are caused by precancerous conditions that could one day turn into cancer, and start growing into nearby tissue or spreading to other parts of the body.
Cervical intraepithelial neoplasia is one such precancerous condition that can show up on a Pap smear. Low-grade cervical intraepithelial neoplasia is less likely to turn into cancer. The presence of these cells on a Pap smear result is called a low-grade squamous intraepithelial lesion. You and your doctor should keep a close eye on it, such as by scheduling a repeat Pap test. High-grade cervical intraepithelial neoplasia is somewhat more likely to turn into cancer. The presence of these cells on a Pap smear result is called high-grade squamous intraepithelial lesion. Your doctor may recommend doing a more accurate examination of your cervix using colposcopy.