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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
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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.
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© Macmillan Cancer Support 2016
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