A caregiver providing comfort to a cancer patient

Cancer

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. 

The most common types of cancer (other than basal cell skin cancer and squamous cell skin cancer) are breast cancer, lung cancer, prostate cancer, colon and rectal cancer, and melanoma.

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.

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.

  • 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.

  • 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 safe sex, and check your home for radon to see if you need a radon mitigation system.

  • 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.

  • 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.

Key Terms

Virtual doctor appointment for cancer patient at home
What to Know About Cancer and COVID-19
Asian man video chatting with doctor at home
What to Know About Telehealth for Testicular Cancer
Woman at home having online consultation with doctor
What to Know About Telehealth for Ovarian Cancer
Senior woman on a video telemedicine call with a doctor at home
What to Know About Telehealth for Cervical Cancer
Close up of a mature woman consulting with her doctor online on her laptop
What to Know About Telehealth for Breast Cancer
Farmer with protective suit manual pesticide sprayer on her plantation
Does Glyphosate Cause Cancer?
Doctor sharing bad news with family member
How Many People Die From Cancer Each Year?
stem cells
What Are Cancer Stem Cells?
Map of the USA
Cancer Statistics and Facts in the United States
melanoma cancer cells
Early Signs of Cancer by Type
Thyroid Cancer Checkup
What to Know About Lymph Nodes and Cancer
oral DNA swab
What Is Genetic Testing for Cancer?
Woman chopping salad greens
Do Cancer-Fighting Foods Work?
Female doctor in discussion with senior male patient and adult daughter in exam room - stock photo
Is Cancer Contagious?
Carcinoid Cancer Awareness ribbon zebra stripe pattern on helping hand support and old aged wood
What Is Carcinoid Cancer?
An ethnic senior woman battling cancer sits with her daughter on the couch
What is Adenocarcinoma?
Doctor touching patient's arm in encouragement
What Happens When Cancer Spreads
Soursop
Can Soursop Help Fight Cancer?
diagram of cancer cells
Why Doesn't the Body Get Rid of Cancer Cells?
photo of many different berries held in a woman's hands
What Exactly Are Free Radicals and Why Are They Important?
Back Pain. Sport injury.
When Cancer Spreads to Your Bones
A picture of a man and a woman having a serious talk
How to Encourage a Cancer Screening
image of the human body with the location of lymph nodes
Understanding the Purpose of Lymph Nodes in the Body
Male friends talking while sitting in living room
How to Tell Someone You Have Cancer
diagram of a blood vessel with a blood clot
Preventing Blood Clots During Cancer Treatment
vials of blood donated by a cancer survivor
Can I Donate Blood if I Have Had Cancer?
Artistic rendering of a cancer cell surrounded by smaller T-cells, or T-lymphocytes.
The Role of T-Cells in Cancer
3d illustration of a cancer cell in the process of mitosis
A Closer Look at the Top 5 Deadliest Cancers
female physician talking to patient
Why Do Some Cancers Come Back?
Understanding A Chemorefractory Cancer
Understanding What Chemorefractory Means
Cancer Research
When Was Cancer First Discovered?
Man sick in bed with a cold
What Being Immunocompetent Actually Means for Your Immune System
image of cancer cells in the body
Paraneoplastic Syndrome Common Types and Symptoms
cancer cells under the microscope may correlate with tumor marker levels
What are Tumor Markers?
Doctor explaining carcinoma in situ to a patient
What Does the Term Carcinoma In Situ Mean?
Female doctor and bald cancer patient talking in clinic examination room
How Common Are Second Primary Cancers?
Doctor with a patient
How Long Can You Wait to Have Surgery for Breast Cancer?
Pancreas
What You Should Know About the IPMN Tumor
Xray showing pleural effusion
Know the Symptoms of Chylothorax in the Lungs
Brain and spinal cord, the site of leptomeningeal metastases
Leptomeningeal Disease Symptoms, Diagnosis and Treatment
Doctors looking at a lung X-ray
What Are Carcinoid Tumors of the Lung?
Woman cancer patient in the hospital
How Health Disparities Can Impact HPV-Related Cancers
Sitting in office, doctor has serious conversation with patient
Heart Cancer: Understanding Cardiac Tumors and Cancers
Imaging evaluation is crucial in confirming a diagnosis
Learn Why You May Develop Spinal Cord Compression From Cancer
woman with skin rash on arm
Tarceva Cancer Drug Uses and Side Effects
Can Megace Treat HIV Wasting?
Man receiving radiation therapy for cancer treatment
Learn How Palliative Radiation Therapy Is Used for Cancer
cancer2.jpg
Hearing Loss After Cancer
Doctor dermatologist examines the subcutaneous wen on the patient's arm, close-up. Skin cancer, malignancy disease concept - stock photo
Benign Tumor: Overview and More
black woman holding cell phone by water
Do Cell Phones Cause Cancer?
metformin tablet
Does Metformin Cause Cancer?
Oil refinery on Mississippi River near New Orleans, Louisiana
Cancer Clusters Along the Mississippi River
brewed yerba mate tea with leaves
Yerba Maté and Cancer
close up of woman sweetening coffee
Aspartame and Cancer: What's The Risk?
air fryer with french fries
Can Air Fryers Cause Cancer?
Engineer at wind turbine farm
Can Windmills Cause Cancer?
Blister pack of medication
What Is The Risk of Zantac Cancer?
woman taking pill
Omeprazole: Cancer Risk and Alternatives
Baby powder on mother's hand, dust dangerous for health concept.
Does Baby Powder Cause Ovarian Cancer?
Farmer spraying crops
Does Roundup Cause Cancer?
Page Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. National Cancer Institute. Common cancer types. Updated September 25, 2020.

  2. American Cancer Society. Lifetime risk of developing or dying from cancer. Updated January 13, 2020.

  3. Aytes A, Giacobbe A. NSD2 is a conserved driver of metastatic prostate cancer progression. Nat Commun. 2018 Dec 5;9(1):5201. doi:10.1038/s41467-018-07511-4

  4. McDonald OG, Li X. Epigenomic reprogramming during pancreatic cancer progression links anabolic glucose metabolism to distant metastasis. Nat Genet. 2017 Mar;49(3):367-376. doi:10.1038/ng.3753

  5. Sanner T, Grimsrud TK. Nicotine: carcinogenicity and effects on response to cancer treatment – a review. Front Oncol. 2015;5. doi:10.3389/fonc.2015.00196

  6. American Cancer Society. Questions people ask about cancer. Updated 

    National Cancer Institute. What is cancer? Updated February 9, 2015.

  7. American Cancer Society. Family cancer syndromes. Updated January 4, 2018.

Additional Reading