What is cancer?
Cancer isn't just one disease. It is a large and complex family of malignancies that can affect virtually every organ in the body. Cancer can strike at any age, although it is most common in people over 50.
More than 1.2 million new cases are diagnosed every year, with half of them occurring in the:
The good news is that cancer death rates have been declining in recent years, especially among men. Men generally experience higher rates of cancer than women. Increasing public awareness has resulted in more people getting regular cancer screenings and practicing healthy lifestyles to reduce their risk.
How does cancer begin?
Cancer begins in the body's cells, which are constantly dividing and multiplying to replace old, damaged cells. Sometimes, cells divide and form excess tissue known as a tumor. In most cases, tumors are benign (non-cancerous). Benign tumors may cause health problems due to their size and location, but are not life-threatening.
However, if an abnormal cell begins to divide, it eventually forms a malignant (cancerous) tumor. Most malignant tumors grow quite rapidly and can take over nearby organs and tissues. Cancerous cells can also travel through the bloodstream to other regions of the body. When cancer spreads from its original site, the process is known as metastasis.
Types of cancer
There are many different types of cancer. Several factors, including the location and how cancerous cells appear under a microscope, determine how cancer is diagnosed. For example, there are several forms of breast cancer. They are classified according to where the tumors originate within the breast and their tendency to invade surrounding organs and tissue.
All cancers fall into one of four broad categories:
- Carcinomas are tumors that arise in the tissues that line the body's organs. About 80% of all cancer cases are carcinomas.
- Sarcomas are tumors that originate in bone, muscle, cartilage, fibrous tissue or fat.
- Leukemias are cancers of the blood or blood-forming organs.
- Lymphomas affect the lymphatic system (a network of vessels and nodes that acts as the body's filter). The lymphatic system distributes nutrients to blood and tissue and prevents bacteria and other foreign "invaders" from entering the bloodstream. There are more than 20 types of lymphoma.