Carcinoma of Unknown Primary

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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. … Read More

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Carcinoma of Unknown Primary

Carcinoma of unknown primary is a diagnostic term given to cancer that has been diagnosed whose primary site can’t be located. In other words, at the time of diagnosis, it has moved away from the site of origin, and was diagnosed in a new site. Usually, cancer is diagnosed at the spot of development (known as a primary tumour). Even if cancer has spread before diagnosis, the site might still be discovered too. However, in the case of carcinoma of unknown primary, the cancer cells are found where they spread to in the body, but their primary tumour can’t be located; which is of important consideration when choosing the most appropriate treatments.  So, when carcinoma of unknown primary is diagnosed, doctors work so hard to try to identify the site of the primary tumour. For an accurate finding, risk factors, symptoms, and results from exams, imaging tests and pathology tests are carefully considered. Diagnosis of Carcinoma of Unknown Primary To diagnose carcinoma of unknown primary, investigations are carried out based on the secondary site of cancer and, if there are any clues, where cancer may have begun. The following investigations may be conducted;  
  • Physical exam: Signs and symptoms are taken note of, and the area of concerns are examined to gather clues about the diagnosis.
  • Blood tests: To examine the number and type of blood cells, and measure the level of certain blood chemicals, known as tumour markers. 
  • Urine test: To detect abnormal cells or check for any problems with organs like the kidneys or bladder. 
  • Biopsy: Small samples of tissue from the secondary tumour or enlarged lymph are taken for examination under a microscope. 
  • Endoscopy: An instrument known as endoscope is inserted into the body via the mouth or nose to get a view of the inside of the body and remove small tissue samples for examination. 
  • Imaging tests: Such as, X-rays, ultrasounds and CT of the abdomen and pelvis, mammogram, MRI and PET scans produce quality pictures of the inside of the body, which is used for assessment.
Treatment of Carcinoma of Unknown Primary After the thorough assessment and careful consideration, a personalized treatment plan is designed, based on patient’s preference, overall general health, and stage of cancer.
  • Chemotherapy: This involves the use of very strong drugs to destroy cancer cells. It may be given through an IV or taken as a take a pill by mouth.
  • Surgery: The removal of cancer alongside some healthy tissue around it.
  • Radiation therapy: The use of high energy X-rays or other forms of radiation to kill cancer cells. The radiation may be given through a machine, or with the aid of a needle, wire, or tiny sealed seed.
  • Hormone therapy: If hormones are thought to play a part in cancer formation, the amount of the said hormone being produced are reduced and the ones already produced are rendered inactive. This can be done with drugs, surgery or radiation.
  • Targeted therapy: Drugs or other substances are given to attack the cancer cells without causing harm to the rest of the body.
  • Immunotherapy (biologic therapy): This treatment is used to boost the immune system or to attack cancer cells.
  • Supportive (palliative) care: This is specialized medical care with a special focus on providing relief from pain and other symptoms of a serious illness.


The symptoms displayed as a result of carcinoma of unknown primary depend on the part of the body involved. In general, however, the following symptoms may be present;

  • A lump felt through the skin.
  • Pain; in the bone, back, legs and hips.
  • Changes to bowel habits; for instance, persistent constipation or diarrhoea.
  • Frequent urination.
  • Cough.
  • Fever and night sweats.
  • Unintended weight loss.
  • Swollen lymph nodes.
  • Development of a mass in the belly.
  • Feeling full.
  • Shortness of breath.
  • Anaemia.
  • Weakness and fatigue.
  • Hoarseness.
  • Bleeding or discharge.

NOTE: There are chances symptoms may be absent, and carcinoma of unknown primary will only be discovered after a medical test for a different reason entirely.



The exact cause of carcinoma of unknown primary or any form of cancer is yet to be discovered. However, it is attributed to changes in the DNA which leads to uncontrollable multiplication of cells, which continue to live after normal cells die

In the case of carcinoma of unknown primary, the cancer cells that have spread to the other parts of the body are what is discovered. The original tumour itself isn't found.

This can be because;

  • The original cancer is too small for detection by imaging tests.
  • The original cancer has been killed by the body's immune system.
  • The original cancer has been removed, knowingly or unknowingly, in an operation for another condition.

In general, cancer forms when cells develop changes (mutations) in their DNA. The DNA contains instructions that tell cells what to do. Certain mutations can cause a cell to multiply uncontrollably and to continue living when normal cells would die. When this happens, the abnormal cells accumulate and form a tumor. The tumor cells can break away and spread (metastasize) to other parts of the body.

In carcinoma of unknown primary, the cancer cells that spread to other parts of the body are found. But the original tumor isn't found.

This can happen if:

• The original cancer is too small to be detected by imaging tests
• The original cancer was killed by the body's immune system
• The original cancer was removed in an operation for another condition


What are the risk factors of Carcinoma of Unknown Primary?

Though not definitive, but the risk of carcinoma of unknown primary might be related to:

  • Old age: It is most likely to occur in those above 60 years.
  • Family history of cancer: There's some evidence linking carcinoma of unknown primary to a family history of cancer that affects the lungs, kidneys or colon.

Are there any coping or supporting tips for Carcinoma of Unknown Primary?

It may be helpful to;

  • Learn enough about cancers to help you make decisions about your care.  
  • Keep friends and family close. They can provide the practical support you'll need when dealing with cancer.
  • Find someone to talk to. Having someone around who is a good listener and willing to hear you talk about your hopes and fears can be really calming. 
  • Join support groups.

What hinders recovery from carcinoma of unknown primary?

The chances of recovery from a carcinoma of unknown primary depend on the following;

  • Where the cancer developed in the body and how far it has spread.
  • The number of organs that has been affected.
  • The look of the tumour cells when viewed under a microscope.
  • The sex of the patient.
  • Whether the cancer is newly diagnosed or recurring (come back, that is).

Is carcinoma of unknown primary one and whole?

There are about 5 classifications of carcinoma of unknown primary

  • Adenocarcinomas of unknown primary: This term is used to classify cancers that develop from the gland cells. Lungs, pancreas, breast, prostate, stomach, liver, or colon are often likely to be the primary sites.
  • Poorly differentiated carcinoma: These are cancer cells that did not develop in enough detail to identify the type of the cancer.
  • Squamous cell cancer: These cells are characterised by a flattened shape like that of the skin cells or cells on the lining of some organs.
  • Poorly differentiated malignant neoplasm
  • Neuroendocrine carcinoma: Cancers that develop in the neuroendocrine system turn the cells into nerve cells and hormone secreting cells.

How can I prevent carcinoma of unknown primary? 

There are no specific preventive measures to this disease. However, having a generally healthy lifestyle – such as not smoking, maintaining a healthy and balanced diet and weight, and cutting out alcohol consumption – may be very protective. 

What is the prognosis of carcinoma of unknown primary?

The exact course of a carcinoma of unknown primary can’t be predicted. It depends on individual circumstances. However, an estimated guess of the likely outcome can be made based on the test results, the rate of tumour growth, age, fitness and medical history. 

Although most carcinoma of unknown primary can't be permanently cured, treatment can, however, keep them under control for months or even years.