Page "Metastasis" Paragraph 28

It is theorized that metastasis always coincides with a primary cancer, and, as such, is a tumor that started from a cancer cell or cells in another part of the body.

However, over 10 % of patients presenting to oncology units will have metastases without a primary tumor found.

In these cases, doctors refer to the primary tumor as " unknown " or " occult ," and the patient is said to have cancer of unknown primary origin ( CUP ) or unknown primary tumors ( UPT ).

It is estimated that 3 % of all cancers are of unknown primary origin.

Studies have shown that, if simple questioning does not reveal the cancer's source ( coughing up blood —" probably lung ", urinating blood —" probably bladder "), complex imaging will not either.

In some of these cases a primary tumor may appear later.