There are so many different kinds/types of this disease it is hard to focus on just one.
With that in mind I have listed (a short list, I assure you) some here to give an idea.
Please visit the American Cancer Society Home Page for descriptions/explanations of these and other ailments.
adrenal cortical cancer
bile duct cancer
brain: cns tumors in children and adults
breast: several types
childhood non-hodgkin's lymphoma
ewing's family of tumors
gastrointestinal carcinoid tumors
gastrointestinal stromal tumors
gestational trophoblastic disease
leukemia: several types
Quite simply, the definiton of cancer is:
Abnormal cells in a part of the body that begin to grow out of control.
Cancer is a complex group of over 100 diseases. Cancer diseases share the common feature of uncontrolled spreading of malignant (harmful) cells in the human body.
Under normal conditions, the cells in the human body divide and grow in an orderly, controlled manner. Cancer occurs when cells grow in an uncontrolled manner, forming a mass of tissue. This mass of tissue is called either a tumor or a lesion.
A cancerous tumor is called a malignant tumor. Malignant tumors can spread to surrounding tissue. Cells from malignant tumors also can break away from the tumor, usually by way of the bloodstream. These cells can travel to other parts of the body, where new tumors may form. This is how cancer spreads. The term for this spreading is metastasis. A tumor which forms this way always consists of cells identical to those of the original tumor.
Not all tumors are cancerous. When a tumor is not cancerous, it is called a benign tumor. Benign tumors often can be removed with surgery and usually do not come back. The cells in benign tumors do not invade other tissues or spread to other parts of the body. In other words, these tumors do not spread, or metastasize.
In most cases, the cause of a cancer is unknown. However, we do know that for some types of cancer, certain risk factors seem to make some people more likely to develop them. Many questions remain unanswered as to why other people can have the same risk factors and never get cancer.
There is no typical way to feel when you are told that you have cancer. Everyone feels and responds differently. Some people experience several emotions at once, ranging from fear, sadness—even anger—to motivation and determination.
There is, however, one feeling that seems consistent for many people who are diagnosed with cancer—and that is a loss of control. One way to regain a sense of control in your life is to learn as much as you can about your disease and treatment options, so you can discuss them openly with your healthcare team.
by The National Cancer Institute
(education and advocacy organization located in San Francisco, California)
Cancer Center: Treatment Hospitals
Don't worry, there are more links coming.