Some types of cancer can be found before they cause symptoms. Checking for cancer (or for conditions that may lead to cancer) in people who have no symptoms is called screening. Screening can help doctors find and treat some types of cancer early. Generally, cancer treatment is more effective when the disease is found early. However, not all types of cancer have screening tests and some tests are only for people with specific genetic risks.

Diagnosis is not the same as detection. Cancer may be detected when symptoms or abnormalities, such as a lump or growth, are recognized by a patient or doctor. After a cancer is detected, it still must be carefully diagnosed.   A diagnosis is an identification of a particular type of cancer. When making a diagnosis, the initial signs and symptoms are investigated through a variety of tests in order to identify whether cancer is causing them and, if so, what type of cancer it is. For example, breast cancer may be detected when a patient notices a lump, but it must be carefully evaluated with a number of tests in order to determine an accurate diagnosis. The diagnosis describes what type of breast cancer it is (i.e. “ductal” if it started in the ducts of the breast or “lobular” if it started in the lobes) and how advanced it is.