Cancer is named from the place it originates. This makes a difference on what type of treatments will be effective. Being diagnosed with cancer of the unknown primary (CUP) means that cancer has been found in the body but the place of origin is unknown.

If later, the place of origin is found then the type of cancer diagnosis changes from an unknown primary to the specific organ or body area that the disease first began.

Some cases of cancer of the unknown primary are unfortunately never found. Physicians will then decide on the best course of treatment based on two factors: The way the cells look under the microscope and which organs are currently involved.

Statistics and Prognosis:

The exact number of cases of this disease is not known. It may be about 2% to 5% of all cancers in the United States. It is found more often among men than among women. The average age of people with this cancer is about 60 years.

This is a very dangerous cancer. Only half of patients will live 9 to 12 months after their cancer is found. There are several reasons why this cancer is so serious. First, most of these are fast-spreading cancers. Second, because the exact type is not known, it is harder for doctors to know what treatment is best. Also, the cancer is often widespread, making it harder to cure.

In recent years, microscopic and other diagnostic techniques have improved dramatically. For this reason, doctors can now determine the primary site in about four out of five cases.