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Our website is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Ⓒ 2024 Dotdash Media, Inc. — All rights reserved Health A-Z Cancer Symptoms Causes & Risk Factors Diagnosis Treatment Living With Support & Coping Prevention Bladder Cancer More Brain Tumors Breast Cancer Leukemia Lung Cancer More Cancer Types Cervical Cancer Childhood Cancer Colon Cancer Gastric Cancer Head & Neck Cancer Liver Cancer Lymphoma Multiple Myeloma Ovarian Cancer Pancreatic Cancer Prostate Cancer Skin Cancer Testicular Cancer Thyroid Cancer Medically reviewed by Jason DelCollo, DO Updated on March 03, 2023 Cancer is a group of over 200 different diseases in which abnormal cells multiply uncontrollably, destroying body tissues or functions. Cancer can form in almost any place in the body and each cancer is named for the tissue type or organ in which it begins. Cancer has various symptoms and is treated in different ways depending on the type. Treatments include surgery, chemotherapy , radiation , and immunotherapy . One in two men and one in three women are expected to develop cancer (not including skin cancer) over the course of a lifetime. Understanding Cancer Cancer: Learning What You Need to Know How to Encourage a Cancer Screening Cancer Facts and Statistics: What You Need to Know A Closer Look at the Top 5 Deadliest Cancers Cancer Cells vs. Normal Cells: How Are They Different? Causes and Risk Factors Do You Know the Leading Causes and Risk Factors of Cancer? Why Doesn’t the Body Get Rid of Cancer Cells? What Exactly Are Free Radicals and Why Are They Important? Is It Possible to Catch Cancer? Frequently Asked Questions What causes cancer? For a normal cell to become a cancer cell , a series of genetic mutations needs to take place. Environmental or medical radiation, carcinogens , infections, genetic makeup, can raise your risk of mutations. Some substances and exposures directly damage DNA, while lifestyle factors (e.g. poor diet or lack of physical activity) can increase cancer risk by decreasing immune defenses. Recent data shows that the metastatic process is mainly caused by epigenetic factors. Learn More Causes and Risk Factors for Cancer Does nicotine cause cancer? Whether or not nicotine directly causes cancer remains unclear, but it’s well established that it’s an addictive ingredient in tobacco products. Research also suggests that nicotine may play a role in accelerating cancer growth.   Smoking tobacco or using smokeless tobacco products exposes you to cancer-causing substances and can weaken the immune system, making it harder to fight the disease. Learn More The Link Between Nicotine and Cancer How does cancer kill you? Cancer cells can divide uncontrollably and may locally invade or spread at distance and affect important organs, such as the lungs or liver, or interfere with body functions and systems that are essential for survival. Cancer cells are also good at evading the immune system and can go undetected by the body’s built-in defenses.   How many stages of cancer are there? Most types of solid cancer have four stages. Stage 1 is the least advanced and stage 4 is the most advanced with the worst prognosis. A common system that is used to determine the stage of solid tumors is the TNM system. It assigns values after tests have evaluated the primary tumor (T value), whether or not it has spread to lymph nodes (N value), and whether or not it has spread to other areas of the body (M value). How do you prevent cancer? Things you can do to help reduce your risk of cancer are to quit or avoid smoking, limit alcohol, exercise regularly, use sun protection, eat a healthy diet high in fruits and vegetables and low in red meat, practice safer sex, and check your home for radon to see if you need a radon mitigation system. Learn More 10 Lifestyle Changes to Help Prevent Cancer Can a blood test detect cancer? They can contribute to a cancer diagnosis, but, in general, are not used to definitely diagnose. Tests may include a complete blood count, a blood chemistry profile, tumor markers, and circulating tumor DNA (currently used only for research purposes). In some forms of blood cancer, other tests like flow cytometry, immunoelectrophoresis, and cytogenetic analysis are used. Learn More How Cancer Is Diagnosed Is cancer hereditary? Most cancers are related to gene mutations that are acquired and are not inherited. However, in 5% to 10% of cases, cancer is related to a family cancer syndrome that can be inherited.   Inherited family syndromes are often mutations in tumor suppressor genes that control how quickly cells divide and when they die. Learn More Causes and Risk Factors of Cancer Types Primary Cancer vs Secondary Cancer How Does Carcinoma Differ From Other Cancers? What Does the Term Carcinoma In Situ Mean? What Is Adenocarcinoma? Diagnosis How Is Cancer Diagnosed? Early Signs of Cancer by Type What Is Genetic Testing for Cancer? What are Tumor Markers? What to Know About Lymph Nodes and Cancer Key Terms Carcinoma Chemotherapy DNA Repair Immunotherapy Malignant Metastasis Radiation Carcinoma Carcinomas are the most common category of malignant solid tumors, accounting for 85% to 95% of cancers. They form in epithelial cells, which are in skin and line the body’s cavities and organs. The other category are hematological malignancies that account for approximately 10% of cancers and sarcomas, which occur in connective tissue , and account for 1% of cancers in adults and 15% cancers in children. Sarcoma vs. Carcinoma: Differences and Similarities Chemotherapy Chemotherapy uses medications to treat cancer. These drugs can interfere with rapid cell division and reduce the size of tumors. Chemotherapy agents may be injected or taken orally. Common side effects may include hair loss, bone marrow suppression, and nausea. Chemotherapy for Cancer DNA Repair The processes cells use to repair DNA damage. Cells have mechanisms to check the DNA before replicating, but when these mechanisms fail, it can lead to mutations and may predispose you to cancer. The activity of DNA repair genes can also influence how effective therapies, such as chemotherapy and radiation, may be in treating cancer. Immunotherapy Immunotherapy refers to treatments for cancer that target the immune system. Examples of immunotherapies...