Patient Compass-Cancer

This is a space to share what other patients have learned along the way — the small, practical things that don't always make it into doctor's appointments but can make a real difference day to day.

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There are two types of tests you may encounter: "screening tests" and "diagnostic tests" — and the difference between them can be confusing.

A screening test is used to detect whether you may be at higher risk for a diagnosis, while a diagnostic test is used to give you a clearer answer about whether a condition is actually present. Importantly, the same medical test can be used for either purpose.

For example, all women are advised to get a screening mammogram at a certain age. If something concerning is seen on the image, they are sent for further testing. A diagnostic mammogram feels exactly the same to the patient — it is still the same mammogram — but it is done when there is already some concern that cancer may be present. In that case, the staff and doctor may have been asked to pay particular attention to a specific area of the breast.

This can happen with other tests too. A person may have a screening colonoscopy simply because they have reached a certain age. But during the procedure, the doctor may discover a mass and biopsy it — and that biopsy may come back showing cancer. What began as a routine screening test has now essentially become diagnostic.

It is also worth noting that some tests are only used for screening. For example, blood tests that look for biochemical markers — such as CA-125, which is associated with ovarian cancer — are used to flag potential concern, not to confirm a diagnosis. These markers can be elevated for many reasons, which is why they signal the need for further testing rather than a diagnosis. Other tests are always diagnostic, meaning their entire purpose is to give a definitive answer. A biopsy is the clearest example — it is never done "just in case." It is done because there is already enough concern to warrant a direct look at the tissue.

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Cancer results can be overwhelming. There are so many different types and there are a lot of confusing terms on each one. This list isn't comprehensive, but we try to touch on the major ones.