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Cancer is a group of diseases involving abnormal cell growth, with the potential to invade or spread to other parts of the body.^[1][2] Cancer are different than benign tumors, which do not spread.^[2]

Possible signs and symptoms include a lump, abnormal bleeding, prolonged cough, unexplained weight loss, and a change in bowel movements.^[3]

Symptoms - Other reasons

While these symptoms may indicate cancer, they can also have other causes.^[3] More than 100 types of cancers affect humans.^[2]

Tobacco use is the cause of about 22% of all cancer deaths.^[1]

Other Causes 1

Another 10% are due to obesity, poor diet, lack of physical activity, or excessive drinking of alcohol.^[1][4][5]

Other Causes 2

Other factors include certain infections, and exposure to ionizing radiation, and environmental pollutants.^[6]

Infectious Causes

In the developing world, 15% of cancers are due to infections such as Helicobacter pylori, hepatitis B, hepatitis C, human papillomavirus infection, Epstein–Barr virus, and HIV.^[1]

Pathophysiology

These factors act, at least partly, by mutation of the genes of a cell.^[7] Typically, many genetic changes are required before cancer develops.^[7] Approximately 5–10% of cancers are due to inherited genetic defects from a person's parents.^[8]

When cancer is suspected because of signs and symptoms, or screening tests, ^[1] it will be further investigated by medical imaging, and confirmed by biopsy.^[9]

Many cancers can be prevented by not smoking, and maintaining a healthy weight.^[10]

Other preventative measures

Limiting alcohol use, eating plenty of fruits, vegetables, and whole grains, as well as avoiding red meat and excessive sunlight, all lower the risk of cancer.^[10][11]

Vaccination

Vaccination against certain infectious diseases such as the human papilloma virus, decreases the risk of cancer.^[12]

Screening

Early detection through screening is useful for cervical and colorectal cancer.^[13]

Screening 2

The benefits of screening in breast cancer are controversial.^[13][14]

Cancer is usually treated with some combination of radiation therapy, surgery, chemotherapy, or targeted therapy.^[1][15]

Pain Management

Pain, and symptom management are an important part of care.^[1] Palliative care is particularly important in people with advanced disease.^[1]

Survival

The chance of survival depends on the type of cancer, and extent of disease at the start of treatment.^[7] In children under 15 at diagnosis, the five-year survival rate in the developed world is on average 80%.^[16] For all cancers in the United States, the average five-year survival rate is 66%.^[17]

Females

In females, the most common types are breast cancer, colorectal cancer, lung cancer, and cervical cancer.^[7] If skin cancer, other than melanoma, were included in total new cancer cases each year, it would account for around 40% of cases.^[18][19]

Males

The most common types of cancer in males are lung cancer, prostate cancer, colorectal cancer, and stomach cancer.^[20]

Children

In children, acute lymphoblastic leukemia and brain tumors are most common, except in Africa where non-Hodgkin lymphoma occurs more often.^[16] In 2012, about 165,000 children under 15 years of age were diagnosed with cancer.^[20]

Global risk

The risk of cancer increases significantly with age, and many cancers occur more commonly in developed countries.^[7] Rates of cancer are increasing, as more people live to an old age, and as lifestyle changes occur in the developing world. These changes will challenge health care in the decades to come.^[21]