Summary
Cancer begins in your cells, which are the building blocks of your body. Normally, your body forms new cells as you need them, replacing old cells that die. Sometimes this process goes wrong. New cells grow even when you don't need them, and old cells don't die when they should. These extra cells can form a mass called a tumor. Tumors can be benign or malignant. Benign tumors aren't cancer while malignant ones are. Cells from malignant tumors can invade nearby tissues. They can also break away and spread to other parts of the body.
Cancer is not just one disease but many diseases. There are more than 100 different types of cancer. Most cancers are named for where they start. For example, lung cancer starts in the lung, and breast cancer starts in the breast. The spread of cancer from one part of the body to another is called metastasis. Symptoms and treatment depend on the cancer type and how advanced it is. Most treatment plans may include surgery, radiation and/or chemotherapy. Some may involve hormone therapy, immunotherapy or other types of biologic therapy, or stem cell transplantation.
NIH: National Cancer Institute
Start Here
Cancer (American Academy of Family Physicians)
Cancer Basics (American Cancer Society)
Also in Spanish
What Is Cancer? From the National Institutes of Health (National Cancer Institute)
Also in Spanish
Diagnosis and Tests
Cancer Screening Overview (PDQ) From the National Institutes of Health (National Cancer Institute)
Also in Spanish
Cancer Staging From the National Institutes of Health (National Cancer Institute)
Also in Spanish
Computed Tomography (CT) Scans and Cancer From the National Institutes of Health (National Cancer Institute)
Also in Spanish
Exams and Test Descriptions (American Cancer Society)
Fine Needle Aspiration (American Academy of Otolaryngology--Head and Neck Surgery)
Pathology Reports From the National Institutes of Health (National Cancer Institute)
Also in Spanish
Sentinel Lymph Node Biopsy From the National Institutes of Health (National Cancer Institute)
Also in Spanish
Tumor Grade From the National Institutes of Health (National Cancer Institute)
Also in Spanish
Tumor Markers From the National Institutes of Health (National Cancer Institute)
Also in Spanish
Understanding Laboratory Tests From the National Institutes of Health (National Cancer Institute)
Also in Spanish
Prevention and Risk Factors
Antioxidants and Cancer Prevention From the National Institutes of Health (National Cancer Institute)
Also in Spanish
Calcium and Cancer Prevention: Strengths and Limits of the Evidence From the National Institutes of Health (National Cancer Institute)
Also in Spanish
Cancer Prevention Overview (PDQ) From the National Institutes of Health (National Cancer Institute)
Also in Spanish
Cancer Vaccines From the National Institutes of Health (National Cancer Institute)
Also in Spanish
Diet Choices to Prevent Cancer (American Academy of Family Physicians)
Also in Spanish
How Is Cancer Risk Measured? From the National Institutes of Health (National Cancer Institute)
Also in Spanish
Risk Factors From the National Institutes of Health (National Cancer Institute)
Vitamin, Mineral, and Multivitamin Supplements for the Primary Prevention of Cardiovascular Disease and Cancer (U.S. Preventive Services Task Force) - PDF
Treatments and Therapies
A to Z List of Cancer Drugs (National Cancer Institute)
Adjuvant Therapy: Treatment to Keep Cancer from Returning (Mayo Foundation for Medical Education and Research)
Angiogenesis Inhibitors From the National Institutes of Health (National Cancer Institute)
Also in Spanish
Biological Therapies for Cancer From the National Institutes of Health (National Cancer Institute)
Also in Spanish
Cancer Alternative Therapies: MedlinePlus Health Topic From the National Institutes of Health (National Library of Medicine)
Also in Spanish
Cancer Surgery: Physically Removing Cancer (Mayo Foundation for Medical Education and Research)
Cancer Treatment Scams (Federal Trade Commission)
Also in Spanish
Hyperthermia in Cancer Treatment From the National Institutes of Health (National Cancer Institute)
Also in Spanish
Lasers in Cancer Treatment From the National Institutes of Health (National Cancer Institute)
Also in Spanish
Managing Cancer Care - Finding Health Care Services From the National Institutes of Health (National Cancer Institute)
Non-Specific Immunotherapies and Adjuvants (American Cancer Society)
Pain Control From the National Institutes of Health (National Cancer Institute) - PDF
Photodynamic Therapy for Cancer From the National Institutes of Health (National Cancer Institute)
Also in Spanish
Targeted Cancer Therapies From the National Institutes of Health (National Cancer Institute)
Also in Spanish
Treatment Option Overview (Carcinoma of Unknown Primary) From the National Institutes of Health (National Cancer Institute)
Also in Spanish
Treatment Option Overview (Extragonadal Germ Cell Tumors) From the National Institutes of Health (National Cancer Institute)
Also in Spanish