What causes cancer?

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Cancer is a class of diseases characterized by out-of-control cell growth. There are over 100 different types of cancer, and each is classified by the type of cell that is initially affected.

Cancer harms the body when damaged cells divide uncontrollably to form lumps or masses of tissue called tumors. Tumors can grow and interfere with the digestive, nervous, and circulatory systems and they can release hormones that alter body function. Tumors that stay in one spot and demonstrate limited growth are generally considered to be nonthreatening.

More dangerous, or malignant, tumors form when two things occur:
A cancerous cell manages to move throughout the body using the blood or lymph systems, destroying healthy tissue in a process called invasion
That cell manages to divide and grow, making new blood vessels to feed itself in a process called angiogenesis.

How cancer spreads has something to do with their adhesion properties. Certain molecular interactions between cells and the scaffolding that holds them in place cause them to become unstuck at the original tumor site; they become dislodged, move on and then reattach themselves at a new site.

Symptoms:

Cancer symptoms are quite varied and depend on where the cancer is located, where it has spread, and how big the tumor is. Some cancers can be felt or seen through the skin - a lump on the breast or testicle can be an indicator of cancer in those locations. Skin cancer is often noted by a change in a wart or mole on the skin. Some oral cancers present white patches inside the mouth or white spots on the tongue.
Other cancers have symptoms that are less physically apparent. Some brain tumors tend to present symptoms early in the disease as they affect important cognitive functions. Pancreas cancers are usually too small to cause symptoms until they cause pain by pushing against nearby nerves or interfere with liver function to cause a yellowing of the skin and eyes called jaundice. Symptoms also can be created as a tumor grows and pushes against organs and blood vessels. For example, colon cancers lead to symptoms such as constipation, diarrhea, and changes in stool size. Bladder or prostate cancers cause changes in bladder function such as more frequent or infrequent urination.
As cancer cells use the body's energy and interfere with normal hormone function, it is possible to present symptoms such as fever, fatigue, excessive sweating, anemia, and unexplained weight loss. However, these symptoms are common in several other diseases as well. For example, coughing and hoarseness can point to lung or throat cancer as well as several other conditions.
If cancer spreads to the brain, patients may experience vertigo, headaches, or seizures. Spreading to the lungs may cause coughing and shortness of breath. In addition, the liver may become enlarged and cause jaundice and bones can become painful, brittle, and break easily.
There are five broad groups that are used to classify cancer.
Carcinomas are characterized by cells that cover internal and external parts of the body such as lung, breast, and colon cancer.
Sarcomas are characterized by cells that are located in bone, cartilage, fat, connective tissue, muscle, and other supportive tissues.
Lymphomas are cancers that begin in the lymph nodes and immune system tissues.
Leukemia’s are cancers that begin in the bone marrow and often accumulate in the bloodstream.
Adenomas are cancers that arise in the thyroid, the pituitary gland, the adrenal gland, and other glandular tissues.

Cancer treatment depends on the type of cancer, the stage of the cancer, age, health status, and additional personal characteristics. There is no single treatment for cancer, and patients often receive a combination of therapies and palliative care. Treatments usually fall into one of the following categories: surgery, radiation, chemotherapy, immunotherapy, hormone therapy, or gene therapy.

Having a healthy diet, being physically active, and maintaining a healthy weight and not

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