WHAT IS CUP?
CUP stands for “Cancer of Unknown Primary”. It may also be called
- occult primary
- metastases of unknown origin (MUO)
- metastatic malignancy of unknown origin
- metastatic cancer of unknown primary
CUP is a type of cancer for which the original (primary) tumour cannot be found.1 The doctors only find metastases (secondary tumours).
WHY IS THE PRIMARY CANCER NOT FOUND?
There are several possible reasons why the doctors may not find the primary tumour in patients with CUP syndrome – even after extensive standard examinations have been performed. It may be that:2
- The primary cancers are very small, grow slowly, and cannot be seen by diagnostic imaging or by the pathological or laboratory workup
- The immune system of the body destroyed the original cancer, or it disappeared for unknown reasons
- The primary cancer was removed, e.g. by surgery for another condition
ARE THERE OTHERS WITH CUP?
About 3–5 percent of all cancer diagnoses are CUPs. It is currently the 10th most common cancer diagnosis in the Western world, of more than 200 types of cancer.1
- Losa F et al. Clinical Translational Oncology 2018; 20: 89–96.
- U.S. Department of Health and Human Services. National Institutes of Health. National Cancer Institute. Carcinoma of Unknown Primary Treatment (PDQ®)–Patient Version. Available at: https://www.cancer.gov/types/unknown-primary/patient/unknown-primary-treatment-pdq (last accessed 13th March, 2020).