Doctors have several methods of making cancer diagnostics, including imaging, genomics, and laboratory tests. Definitive cancer diagnostics usually requires a biopsy. The doctor typically sees something that leads him to suspect cancer, and requests additional tests. Suspicious symptoms that may indicate cancer, or signs he notices during a routine screening test or physical examination, as well as health complaints from the patient may all lead to requests for additional testing.
A biopsy is the most common type of cancer diagnostics test. Biopsies are usually mildly invasive procedures where a doctor removes a small piece of tissue and sends it to a laboratory. A pathologist at the laboratory examines the tissues under a microscope to determine whether the cells are cancerous.
Laboratory tests are used by the doctor once a definitive cancer diagnosis is made. A laboratory technician will examine the blood or urine of the patient to determine certain features of the cancer, such as what stage the cancer is in. These tests are crucial because they help the doctor determine the best way to proceed with treatment.
Some examples of laboratory tests include CBC, blood protein tests, urine cytology, and tumor marker tests. A CBC, or complete blood count, test measures the amount of different blood cells in the body, and is used to diagnose blood cancers. Blood protein tests find abnormalities in immune system proteins, and is used to diagnose multiple myeloma. Urine cytology detects cancer cells in the urine, which indicates the presence of cancer in the bladder, kidneys, or ureters. Tumor marker tests look for chemicals produced by tumors, and include the PSA test to diagnose prostate cancer, HCG to detect ovarian and testicular cancer, and the alpha-fetoprotein test to detect liver cancer.
Imaging tests can also be used for some types of cancer diagnostics. Depending on the area of the body, x-rays, computed tomography (CT) scans, ultrasounds, positron emission tomography (PET) scans, or magnetic resonance imaging (MRI) scans may be recommended. All of these imaging tests provide pictures of what is going on inside the body. Mammograms are a common form of cancer diagnostics that use imaging scans as well.
Sometimes doctors look for changes in certain genes that are associated with the development of cancer. They may perform genomics tests such as fluorescent in situ hybridization, or FISH, tests, or polymerase chain reaction, or PCR, tests. Doctors may run a FISH test when they conduct a breast biopsy. The FISH test indicates whether the patient has extra copies of the HER2 gene, which would indicate a genetic component to breast cancer. PCR tests show promise as an early detection method for lung cancer.