• Also Known As:
  • Malignancy
  • Malignant tumor
Medically Reviewed by Expert Board

This page was fact checked by our expert Medical Review Board for accuracy and objectivity. Read more about our editorial policy and review process.

This article was last modified on
Learn more about...

What is cancer?

Cancer is a disease in which cells in a part of the body become abnormal and grow uncontrollably. Cancerous cells do not go through the natural stages of growth, division, and dying that normal cells do. They multiply unchecked and may form one or more masses of cells (tumors). Tumors can damage healthy tissue and grow large enough to interfere with body functions. However, not all cancers form tumors (e.g., leukemia) and not all tumors are malignant—some are benign (non-cancerous and non-spreading).

Cancer can eventually spread (metastasize) beyond the site of origin into nearby lymph nodes, tissues, and other organs. There are many types of cancer and they are often named according to location in the body where they originate.

Various lab tests are used in the screening, diagnosis, and management as well as the risk assessment of cancer. However, not all types of tests are available for all types of cancer. Below are listed some examples of these types of tests:

  • Risk assessment—determining whether an individual has a high risk for a particular type of cancer; examples include BRCA mutation for breast and ovarian cancer risk and HPV for cervical cancer risk
  • Screening—detecting cancer before symptoms appear; examples include Pap test for cervical cancer
  • Diagnosis—examples include BCR/ABL mutation to help diagnose chronic myelogenous leukemia (CML) or a type of acute lymphoblastic leukemia (ALL) and JAK2 to help diagnose myeloproliferative neoplasms.
  • Treatment—helping to guide the selection of drugs to treat cancer or monitoring effectiveness of treatment; example include HER2/neu to determine whether a woman’s breast cancer will respond to the drug trastuzumab and BCR/ABL to monitor treatment of leukemia

Not all types of cancer are covered on Lab Tests Online, but there are numerous web resources available, some specific to certain types of cancer and others that provide more general information on cancer (see Additional Resources below).

Articles on specific types of cancer 
Breast cancer Melanoma
Cervical cancer Multiple myeloma
Colorectal cancer Myeloproliferative neoplasms
Leukemia Ovarian cancer
Liver cancer Pancreatic cancer
Lung cancer Prostate cancer
Lymphoma Testicular cancer
Waldenstrom Macroglobulinemia Thyroid cancer

Other articles on Lab Tests Online that cover cancer-related topics:


This graph shows the number of new U.S. cancer cases and deaths each year per 100,000 persons by race/ethnicity and sex. Image credit: National Cancer Institute


Leading-edge Research

Research is ongoing into new tests and treatments for cancer. For example, new research has shown that most people with waldenstrom macroglobulinemia (WM) have cancer cells with MYD88 gene mutations. A smaller percentage of WM patients have CXCR4 gene mutations. Scientists are looking into developing new treatments that target these mutations. For more on these, visit the International Waldenstrom’s Macroglobulinemia Foundation website. For more on what’s new in cancer, see the links below in Patient Resources.