Browser does not support script.
Skip to main content
Find out how we produce our information
It can be helpful to read about primary cancers, secondary cancers and cell types. This could help you understand how a cancer can be diagnosed when doctors can't find out where the cancer started.
Understand primary and secondary cancers, and how cancer can spread in the body
Information on cell types and cancer of unknown primary (CUP).
Read about what cancer of unknown primary (CUP) is and possible reasons why the primary cancer can't be found
Save page to
For answers, support or just a chat, call the Macmillan Support Line free* (Monday to Friday, 9am-8pm).
*See information about calling our support line from a mobile.
If you have any questions about cancer, need support or just want someone to talk to, ask Macmillan.
If you have any questions about Macmillan we would love to hear from you .
You can also follow us on Facebook, Twitter, Flickr or YouTube.
© Macmillan Cancer Support 2017
what are these?