Cancer of Unknown Primary: Stages

The stage of a cancer is how much cancer there is and how far it has spread in your body. Your healthcare provider uses exams and tests to find out the size of the cancer and where it is (where it first started or the primary site). Scans can also show if the cancer has grown into nearby areas, and if it has spread to other parts of your body. The stage is one of the most important things to know when deciding how to treat the cancer.

There are different staging systems used for cancer. Most cancers are staged using Roman numerals and can have a value of I (1), II (2), III (3), or IV (4). This is based on if the cancer is still contained in the area where it began, has started to spread into nearby tissues or organs, or has spread to more distant tissues or organs (metastasized).

Stage I is the earliest stage. It usually means the cancer is still contained in the place it first started and hasn't spread. Stage IV is the most advanced stage. In this stage, the cancer has spread from the primary site to other parts of the body.

Unlike other kinds of cancer, there is no staging system for cancer of unknown primary (CUP). If you’ve been diagnosed with CUP, your cancer was found after it had spread from an unknown primary site. Your healthcare providers aren't sure where it first started, even after extensive testing. Because of this, all CUPs are at least a stage II. And it’s likely that they're stage III or IV. Ask your healthcare provider to explain the details of your cancer to you in a way you can understand.

CUP can be hard to stage. Talk with your healthcare provider about what the stage means for you. Ask any questions and talk about your concerns.