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About Cancer

Cancer of unknown primary (CUP)

Cancer of unknown primary means doctors don't know where the cancer first started. They have found cancer spread (secondary cancer) in another part of your body.

It is sometimes called unknown primary cancer or unknown primary tumour.

The tests and treatments for cancer of unknown primary in children and young adults might be different to adults. The information in this section is for adults with CUP.

Last reviewed: 12 Aug 2024

Next review due: 12 Aug 2027

Reviewed by

This section has been written, reviewed and updated by Cancer Research UK’s Patient Information Web Team. Thanks to the expert medical professionals and people affected by cancer who have helped to review this information.

  • Dr Claire Mitchell (Consultant Medical Oncologist)

  • Our lay reviewers

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