Unknown Primary Cancer


From its initial (primary) site, cancers can spread throughout the body to form secondary cancers. Sometimes doctors can diagnose a secondary cancer without being able to locate the primary. Because cancers are usually named after their primary site, this is known as cancer of unknown primary (CUP): a general term for many types of cancer.

On examination of the secondary cancer cells, doctors can sometimes tell where the primary is because they still look like the cells of the primary area, for example, cells from a primary breast cancer that have spread to the liver will still look like breast cancer cells.

Things to look out for

Symptoms of CUP will vary depending on where the secondary cancer or cancers are:

  • Secondary cancer in the lung – a persistent cough, breathlessness or fluid on the lungs
  • Secondary cancer in the bone – a dull, persistent pain in the bone, often worse at night
  • Secondary cancer in the liver – abdominal swelling and discomfort, nausea and loss of appetite, yellowing of the skin and eyes, or fluid collecting in the abdomen
  • Secondary cancer in the lymph nodes (glands) – swollen, hard or painful lymph nodes

General symptoms include:

  • Unexplained weight loss
  • Loss of appetite
  • Constant tiredness
  • Looking pale or feeling breathless due to a lack of red blood cells (anaemia)

All these symptoms can be caused by other conditions but it’s important to have your doctor check them.