Cancer of unknown primary (CUP) occurs when cancer cells have spread in the body and formed metastatic tumors but the site of the primary cancer is not known. Explore the links on this page to learn more about CUP, how it is treated, and clinical trials that are available.

Carcinoma of Unknown Primary Treatment

  • 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.
  • Sometimes the primary cancer is never found.
  • The signs and symptoms of CUP are different, depending on where the cancer has spread in the body.
  • Different tests are used to detect (find) cancer.
  • If tests show there may be cancer, a biopsy is done.
  • When the type of cancer cells or tissue removed is different from the type of cancer cells expected to be found, a diagnosis of CUP may be made.
  • Tests and procedures used to find the primary cancer depend on where the cancer has spread.
  • Certain factors affect prognosis (chance of recovery).

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.

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.

Sometimes CUP does not cause any signs or symptoms. Signs and symptoms may be caused by CUP or by other conditions. Check with your doctor if you have any of 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.

Childhood Carcinoma of Unknown Primary

Cancer can form in any tissue in the body. The first cancer to form is called the primary cancer. The process of cancer cells spreading to other parts of the body is called metastasis. The cancer that has spread to another part of the body is called metastatic cancer.

In carcinoma of unknown primary (CUP), metastatic cancer is diagnosed, but the primary cancer has not been found.

This type of cancer is also called occult primary tumor.

The extent or spread of cancer is usually described as stages. The stage of the cancer is usually used to plan treatment. However, carcinoma of unknown primary (CUP) has already spread to other parts of the body when it is found. There is no standard staging system for CUP.

The primary cancer does not cause signs and symptoms of disease.

Check with your doctor if you have any of the following general signs of cancer:

  • 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.
  • Drenching night sweats.
  • Weight loss for no known reason or loss of appetite.

There are different types of treatment for children with carcinoma of unknown primary.

Some treatments are standard (the currently used treatment), and some are being tested in clinical trials. A treatment clinical trial is a research study meant to help improve current treatments or obtain information on new treatments for patients with cancer. When clinical trials show that a new treatment is better than the standard treatment, the new treatment may become the standard treatment.

What is Cancer?

  • Cancer can start almost anywhere in the human body, which is made up of trillions of cells. Normally, human cells grow and divide to form new cells as the body needs them. When cells grow old or become damaged, they die, and new cells take their place.

  • Cancer prevention is action taken to lower the risk of getting cancer. This can include maintaining a healthy lifestyle, avoiding exposure to known cancer-causing substances, and taking medicines or vaccines that can prevent cancer from developing.

  • Cancer can cause many different symptoms. Most often these symptoms are not caused by cancer, but by benign tumors or other problems. If you have symptoms that last for a couple of weeks, your doctor will do a physical exam and order tests or other procedures to find out what is causing your symptoms.