Our bodies are made of cells, which are constantly duplicating themselves to replace old worn out and dying cells. This process is carefully controlled by the cell's genetic material (its DNA) and other elements to ensure that the cells do not reproduce faster than the old cells wear out. However, occasionally a cell's DNA can become damaged in such a way that it begins reproducing at an abnormal rate. This is what creates a cancer cell.

If the body's natural brakes are turned off, cancer cells grow and multiply without stopping until they form a mass large enough for us to either see or feel directly or detect with special screening tests. Depending on the cancer, it can take years for the mass to grow to a size where it is noticeable in this way.

Diagnosis is different from detection.

When a cancer is found through either a physical exam or a routine screening test such as a mammogram or colonoscopy, the first step is determining what type of cancer it is and how advanced it is.

If you are reading this page because you, your primary care doctor or a routine screening test detected a cancer, you may be wondering how diagnosis works. The information in this section will help you prepare for your treatment. However, it is not meant to replace the individual attention, advice and treatment plan of your oncologist and medical team.

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