Carcinoma of unknown primary


Carcinoma of unknown primary (CUP) is a diagnosis given when the cancer is discovered in the body but unable to pinpoint the origin of a tumor. The cancer has spread to another part of the body and the abnormal cell features do not lead to the discovery of where the disease originated. This condition is also known as occult primary cancer.

Cancer can begin in any tissue of the body. The primary location defines the cancer. If the cancer originates in the liver and travels (metastasizes) to the lungs, it is still referred to as liver cancer, not lung cancer. Cancer alters the appearance of a cell type. Doctors can tell if cancer has spread when they identify abnormal cell types in the organs where they should not be.

If a carcinoma of unknown primary is discovered, clinicians seek to determine the primary tumor site. When determining where the cancer started, the doctor may evaluate the risk factors, symptoms, and the findings of exams, imaging tests, and laboratory testing. The treatment is determined by taking the location of the original tumor into account.


There are no distinct symptoms associated with cancer of unknown primary. The signs and symptoms depend on which portion of the body is affected. Common signs and symptoms include:

  • Pain, especially in the abdomen or chest
  • Any bulge, lump or thickening in the body
  • Cough or hoarseness of voice
  • Constipation, diarrhea, or frequent urination
  • Fever
  • Sweating at night
  • Unexpected weight loss or appetite loss
  • Fatigue
  • Abnormal bleeding or discharge


Cancer can be caused by a variety of factors. It is very difficult to pinpoint a specific cause of carcinoma of unknown primary since the original site of the malignancy is unknown.

Cancer is usually caused by mutations in the DNA of cells. DNA provides instructions that direct cells on what to perform. These abnormal cells then divide, multiply, and possibly spread to other parts of the body. Cancer cells that have spread to other places of the body are observed in carcinoma of unknown primary. However, the primary tumor is not discovered.

Carcinoma of unknown primary can occur if:

  • The origin of the cancer is too minor for imaging tests to detect
  • The immune system of the body killed the original cancer
  • There was a surgery for another condition and the original cancer was unknowingly removed during the operation

Risk factors

There are several factors that affects one’s risk of getting carcinoma of unknown primary, such as:

  • Age: People with ages 60 and older are at a higher risk of getting this disease.
  • Family history of cancer: Family history of lungs, kidney, or colon cancer may be linked to a higher risk of carcinoma of unknown primary.