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Carcinoma of Unknown Primary Treatment (PDQ®): Treatment - Patient Information [NCI] - General Information About Carcinoma of Unknown Primary

Carcinoma of unknown primary (CUP) is a rare disease in which malignant (cancer) cells are found in the body but the place the cancer began is not known.

Cancer can form in any tissue of the body. The primary cancer (the cancer that first formed) can spread to other parts of the body. This process is called metastasis. Cancer cells usually look like the cells in the type of tissue in which the cancer began. For example, breast cancer cells may spread to the lung. Because the cancer began in the breast, the cancer cells in the lung look like breast cancer cells.

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Sometimes doctors find where the cancer has spread but cannot find where in the body the cancer first began to grow. This type of cancer is called a cancer of unknown primary (CUP) or occult primary tumor.

Tests are done to find where the primary cancer began and to get information about where the cancer has spread. When tests are able to find the primary cancer, the cancer is no longer a CUP and treatment is based on the type of primary cancer.

Sometimes the primary cancer is never found.

The primary cancer (the cancer that first formed) may not be found for one of the following reasons:

  • The primary cancer is very small and grows slowly.
  • The body's immune system killed the primary cancer.
  • The primary cancer was removed during surgery for another condition and doctors didn't know cancer had formed. For example, a uterus with cancer may be removed during a hysterectomy to treat a serious infection.

The signs and symptoms of CUP are different, depending on where the cancer has spread in the body.

Signs and symptoms of CUP may include the following:

  • Lump or thickening in any part of the body.
  • Pain that is in one part of the body and does not go away.
  • A cough that does not go away or hoarseness in the voice.
  • Change in bowel or bladder habits, such as constipation, diarrhea, or frequent urination.
  • Unusual bleeding or discharge.
  • Fever for no known reason that does not go away.
  • Night sweats.
  • Weight loss for no known reason or loss of appetite.

Other conditions may cause these same symptoms. Sometimes CUP does not cause any symptoms. Talk to your doctor if you have any of these problems.

Different tests are used to detect (find) cancer.

The following tests and procedures may be used:

  • Physical exam and history: An exam of the body to check general signs of health, including checking for signs of disease, such as lumps or anything else that seems unusual. A history of the patient's health habits and past illnesses and treatments will also be taken.
  • Urinalysis: A test to check the color of urine and its contents, such as sugar, protein, blood, and bacteria.
  • Blood chemistry studies: A procedure in which a blood sample is checked to measure the amounts of certain substances released into the blood by organs and tissues in the body. An unusual (higher or lower than normal) amount of a substance can be a sign of disease in the organ or tissue that makes it.
  • Complete blood count: A procedure in which a sample of blood is drawn and checked for the following:
    • The number of red blood cells, white blood cells, and platelets.
    • The amount of hemoglobin (the protein that carries oxygen) in the red blood cells.
    • The portion of the sample made up of red blood cells.
  • Fecal occult blood test: A test to check stool (solid waste) for blood that can only be seen with a microscope. Small samples of stool are placed on special cards and returned to the doctor or laboratory for testing. Because some cancers bleed, blood in the stool may be a sign of cancer in the colon or rectum.
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WebMD Public Information from the National Cancer Institute

Last Updated: February 25, 2014
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.
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