Cancer of Unknown Primary Origin
Cancer of Unknown Primary Origin
Cleveland Clinic

What is carcinoma of unknown primary?
Carcinoma of unknown primary (CUP) is a disease in which cancer (malignant) cells are found somewhere in the body, but the place where they first started growing (the origin or primary site) cannot be found. This occurs in about 2%-4% of cancer patients.

Actually, CUP can be described as a group of different types of cancer all of which have become known by the place or places in the body where the cancer has spread (metastasized) from another part of the body. Because all of these diseases are not alike, chance of recovery (prognosis) and choice of treatment may be different for each patient.

If CUP is suspected, a doctor will order several tests, one of which may be a biopsy. This means a small piece of tissue is cut from the tumor and looked at under a microscope. The doctor may also do a complete history and physical examination, and order chest x-rays along with blood, urine, and stool tests. A cancer can be called CUP when the doctor cannot tell from the test results where the cancer began.

The pattern of how CUP has spread may also give the doctor information to help determine where it started. For example, lung metastases are more common when cancer begins above the diaphragm (the thin muscle under the lungs that helps the breathing process). Most large studies have shown that CUP often starts in the lungs or pancreas. Less often, it may start in the colon, rectum, breast, or prostate.

An important part of trying to find out where the cancer started is to see how the cancer cells look under a microscope (histology). Other special tests may also be done that help the doctor find out where the cancer started and choose the best type of treatment.

Stage Explanation
Stages of carcinoma of unknown primary
When cancer is diagnosed, more tests are usually done to find out if cancer cells have spread to other parts of the body. This is called staging. But, when CUP is diagnosed, the number and type of tests done may be different for each patient. The treatment options in this summary are based on whether the cancer has just been found (newly diagnosed) or the cancer has come back after it has been treated (recurrent).

The treatment options are also based on where the cancer is found, where the doctor thinks the cancer started, what the cancer cells look like under a microscope, and other factors. A doctor may find that the cancer fits into one of the following groups:

Cancer in the cervical lymph nodes: cancer in the small, bean-shaped organs that make and store infection-fighting cells (lymph nodes) in the neck area
Poorly differentiated carcinomas: the cancer cells look very different from normal cells
Metastatic melanoma to a single nodal site: cancer of the cells that color the skin (melanocytes) that has spread to lymph nodes in only one part of the body
Isolated axillary metastasis: cancer that has spread only to lymph nodes in the area of the armpits
Inguinal node metastasis: cancer that has spread to lymph nodes in the groin area
Multiple involvement: cancer that has spread to several different areas of the body
Treatment Option Overview
How carcinoma of unknown primary is treated
Different types of treatment are available for patients with carcinoma of unknown primary (CUP). 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. Patients may want to think about taking part in a clinical trial. Some clinical trials are open only to patients who have not started treatment.

Some of the standard treatments that are used are:

Surgery (taking out the cancer in an operation)
Radiation therapy (using high- dose x-rays to kill cancer cells)
Chemotherapy (using drugs to kill cancer cells)
Hormone therapy (using hormones to stop the cancer cells from growing)
Surgery is a common treatment for CUP. A doctor may remove the cancer and some of the healthy tissue around it. Different operations are used depending on where the cancer is found. If the cancer has spread to lymph nodes, the lymph nodes may be removed (lymph node dissection). If the nodes involved are in the groin, this operation is called a superficial groin dissection. If the cancer has spread to lymph nodes and also to some surrounding areas, the doctor may have to remove a larger portion of tissue around the nodes. When muscles, nerves, and other tissue in the neck are removed, this is called a radical neck dissection.

Radiation therapy uses x-rays or other high-energy rays to kill cancer cells and shrink tumors. Radiation may be used alone or before or after surgery.

Chemotherapy uses drugs to kill cancer cells. Chemotherapy may be taken by mouth or it may be put into the body by a needle in a vein or muscle. Chemotherapy is called a systemic treatment because the drugs enter the bloodstream, travel through the body, and can kill cancer cells throughout the body. Chemotherapy may be used alone or after surgery. Therapy given after an operation when there are no cancer cells that can be seen is called adjuvant therapy.

Hormone therapy is used to stop the hormones in the body that help cancer cells grow. This may be done by using drugs that change the way hormones work or by surgery that takes out organs that make hormones, such as the testicles (orchiectomy).

Treatment in a clinical trial
For some patients, taking part in a clinical trial may be the best treatment choice. Clinical trials are part of the cancer research process. Clinical trials are done to find out if new cancer treatments are safe and effective or better than the standard treatment.

Many of today's standard treatments for cancer are based on earlier clinical trials. Patients who take part in a clinical trial may receive the standard treatment or be among the first to receive a new treatment.

Patients who take part in clinical trials also help improve the way cancer will be treated in the future. Even when clinical trials do not lead to effective new treatments, they often answer important questions and help move research forward.

Some clinical trials only include patients who have not yet received treatment. Other trials test treatments for patients whose cancer has not gotten better. There are also clinical trials that test new ways to stop cancer from recurring (coming back) or reduce the side effects of cancer treatment.

Clinical trials are taking place in many parts of the country. Check with your doctor for clinical trials that may be right for you.

Newly Diagnosed Carcinoma of Unknown Primary
If the cancer is in the neck area (cervical lymph nodes), treatment may be one of the following:

Surgery to remove the tonsils (tonsillectomy).
Radiation therapy.
Radiation therapy followed by surgery.
Neck surgery (radical neck dissection).
Neck surgery followed by radiation therapy.
If the cancer is a poorly differentiated carcinoma (the cancer cells look very different than normal cells), the treatment will probably be chemotherapy. Surgery or radiation therapy has also been used for patients with neuroendocrine (nervous system and hormonal system) cancer.

If the cancer is peritoneal adenocarcinomatosis (the tumor is in the lining inside the abdomen), the treatment will probably be chemotherapy.

If the cancer is an isolated axillary nodal metastasis, it is likely that the cancer started in the lung or breast. If female, a mammogram (an x-ray picture of the breast) will be used to check for breast cancer. After tests to check for lung and breast cancer, the treatment may be one of the following:

Surgery to remove the lymph nodes with or without surgery to remove the breast (mastectomy) or radiation therapy to the breast.
Treatment as described above plus chemotherapy that is used for breast cancer.
If the cancer is in the inguinal nodes, the treatment may be one of the following:

Surgery to remove the cancer.
Groin surgery (superficial groin dissection).
Surgery to remove some of the tumor (biopsy) with or without radiation therapy, surgery to remove the lymph nodes, or chemotherapy.
If the cancer is melanoma that has spread to a single nodal site, the treatment will probably be surgery to remove the lymph nodes.

If there is cancer in several different areas of the body and the doctor thinks that the origin of the cancer is one for which there is standard systemic therapy, then that therapy should be given. The following are examples:

Hormone therapy for prostate cancer.
Chemotherapy or hormone therapy for breast cancer.
Chemotherapy for ovarian cancer.
If the source of the cancer cannot be found, then the best treatment may not be known. Patients may want to consider taking part in a clinical trial.

Recurrent Carcinoma of Unknown Primary
Treatment of recurrent CUP depends on the type of cancer, what treatment was received before, the part of the body where the cancer has come back, and other factors. A patient may want to consider taking part in a clinical trial.

To learn more
For more information, U.S. residents may call the National Cancer Institute's (NCI's) Cancer Information Service toll-free at 1.800.4.CANCER (1.800.422.6237) Monday through Friday from 9:00 a.m. to 4:30 p.m. Deaf and hard-of-hearing callers with TTY equipment may call 1.800.332.8615. The call is free and a trained Cancer Information Specialist is available to answer your questions.

For more information from the NCI, please write to this address:

NCI Public Inquiries Office
Suite 3036A
6116 Executive Boulevard, MSC8322
Bethesda, MD 20892-8322

Source: National Institutes of Health; National Cancer Institute

This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition. For additional written health information, please contact the Health Information Center at the Cleveland Clinic (216) 444-3771 or toll-free (800) 223-2273 extension 43771 or visit
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