Cancer Research UK on Google+ Cancer Research UK on Facebook Cancer Research UK on Twitter
Skip navigation

Cancer of unknown primary statistics

CUP Stats Doughnut

  • 9,762 people in the UK were diagnosed with cancer of unknown primary in 2011.
  • There were 10,625 deaths from cancer of unknown primary in the UK in 2012.


Stats, info and publications

See our Key Stats for a summary of the main stats and information.

See in-depth statistics for Incidence and Mortality.

Download our publications about these statistics: 

The latest statistics available for cancer of unknown primary in the UK are; incidence 2011 and mortality 2012. Reliable survival data for the UK is currently not available. Find out why these are the latest statistics available.

The ICD codes for cancer of unknown primary are ICD-10 C77-C80.

Cancer of unknown primary (CUP) is an inexact term, making it hard to represent accurately. Patients are recorded as having CUP if the primary site of the malignancy cannot be established or the tumour has been registered without specification of site. Capturing and reporting the incidence of CUP cases can be difficult. In some patients the primary site or the tumour type cannot be determined, even after extensive investigations. In others, patients presenting with wide-spread metastases without an obvious primary site may be too ill to undergo invasive tests or have cancer at such an advanced stage that further investigations would no longer aid their diagnosis or treatment. Both scenarios will lead to patients being registered as CUP. However, some patients, initially diagnosed with CUP, may subsequently have their primary site determined (either during the diagnostic/treatment process or at post-mortem) and will thus no longer be registered and counted as CUP. Finally, a few cases may be misclassified and end up registered as CUP when the clinical or pathological information transmitted to the Cancer Registry is insufficient; for example if the primary site of the malignancy is not indicated on the notes or reports. Due to this unspecific classification the  National Institute for Health and Clinical Excellence (NICE) issued a guideline which stated that the majority of CUP can be covered by the ICD codes ICD-10 C77-C801, so the statistics presented are our best current understanding of the incidence of CUP.

Mortality statistics for CUP are further complicated by the fact that they are compiled separately from cancer registration, at the Office for National Statistics (ONS), and are based solely on the clinical statement of causes of death on the death certificate. Depending on circumstances the clinician completing the death certificate may not be aware of, or have access to, the deceased patient's primary cancer diagnosis or might only state the metastatic spread of the cancer as the cause of death. As ONS have to rely on the death certificate this can lead to higher mortality statistics for more vague ICD-10 codes, which includes the metastatic and unknown primary codes defined as CUP. Thus, CUP mortality figures are, in part, thought to be higher than CUP incidence figures because a cause of death statement of, for example, 'cancer' or 'metastatic liver disease' would result in a CUP mortality code even if the patient was not originally diagnosed with CUP.

Specific questions and answers about some of Cancer Research UK's statistics and information and explanations on terminology used for statistics and reporting of cancer, and the methods used to calculate some of the statistics are also available. 


We would like to acknowledge the essential work of the cancer registries in the United Kingdom and Ireland Association of Cancer Registries, without which there would be no data. 

No Error

Rate this page:
Submit rating
Rated 1 out of 5 based on 1 votes
Rate this page
Rate this page for no comments box
Please enter feedback to continue submitting
Send feedback
Question about cancer? Contact our information nurse team
Updated: 17 September 2014