Written by eHealth Navigator

What is cancer?

Cancer is a group of many related diseases that begin in cells, the body's basic building blocks. To understand cancer, it is helpful to know what happens when normal cells become cancerous. The body is made up of many types of cells. Normally, cells grow and divide to produce more cells as they are needed to keep the body healthy. Sometimes, this orderly process goes wrong. New cells form when the body does not need them, and old cells do not die when they should. The extra cells form a mass of tissue called a growth or tumor.

Not all tumors are cancerous; tumors can be benign or malignant. Benign tumors are not cancer. They can often be removed and, in most cases, they do not come back. Cells in benign tumors do not spread to other parts of the body. Most important, benign tumors are rarely a threat to life. Malignant tumors are cancer. Cells in malignant tumors are abnormal and divide without control or order. Cancer cells invade and destroy the tissue around them. Cancer cells can also break away from a malignant tumor and enter the bloodstream or lymphatic system.

Blood vessels include a network of arteries, capillaries, and veins through which the blood circulates in the body. The lymphatic system carries lymph and white blood cells through lymphatic vessels (thin tubes) to all the tissues of the body. By moving through the bloodstream or lymphatic system, cancer can spread from the primary (original) cancer site to form new tumors in other organs. The spread of cancer is called metastasis.

What are the major types of cancer?

The following table gives the estimated numbers of new cases and deaths for each common cancer type:

                                                                Estimated New                                               Estimated      
Cancer Types                                      Cases Annually                                           Deaths Annually

Bladder                                                            72,570                                                         15,210      
Breast (Female – Male)                     232,340 – 2,240                                              39,620 – 410     
Colon and Rectal (Combined)                 142,820                                                          50,830      
Endometrial                                                   49,560                                                             8,190      
Kidney (Renal Cell) Cancer                        59,938                                                           12,586     
Leukemia (All Types)                                    48,610                                                          23,720     
Lung (Including Bronchus)                       228,190                                                         159,480    
Melanoma                                                       76,690                                                             9,480     
Non-Hodgkin Lymphoma                            69,740                                                           19,020     
Pancreatic                                                      45,220                                                            38,460     
Prostate                                                        238,590                                                           29,720      
Thyroid                                                            60,220                                                              1,850

Cancer incidence and mortality statistics reported by the American Cancer Society and other resources were used to create the list. To qualify as a common cancer for the list, the estimated annual incidence for 2013 had to be 40,000 cases or more.

The most common type of cancer on the list is prostate cancer, with more than 238,000 new cases expected in the United States in 2013. The next most common cancers are breast cancer and lung cancer.

Because colon and rectal cancers are often referred to as "colorectal cancers," these two cancer types are combined for the list. For 2013, the estimated number of new cases of colon cancer and rectal cancer are 102,480 and 40,340, respectively, adding to a total of 142,820 new cases of colorectal cancer.

Kidney cancers can be divided into two major groups, renal parenchyma cancers and renal pelvis cancers. Approximately 92 percent of kidney cancers develop in the renal parenchyma, and nearly all of these cancers are renal cell cancers. The estimated number of new cases of renal cell cancer for 2013 is 59,938.

Types of Tumors?

There are more than 120 types of brain and central nervous system (CNS) tumors. Today, most medical institutions use the World Health Organization (WHO) classification system to identify brain tumors. The WHO classifies brain tumors by cell origin and how the cells behave, from the least aggressive (benign) to the most aggressive (malignant). Some tumor types are assigned a grade, ranging from Grade I (least malignant) to Grade IV (most malignant), which signifies the rate of growth. There are variations in grading systems, depending on the tumor type. The classification and grade of an individual tumor help predict its likely behavior.

Last Updated on Wednesday, 12 February 2014 10:19AM