Carcinoma of Unknown Primary Treatment (PDQ®): Treatment - Patient Information [NCI] - General Information About Carcinoma of Unknown Primary
In some cases, the part of the body where cancer cells are first found helps the doctor decide which diagnostic tests will be most helpful.
When cancer is found above the diaphragm (the thin muscle under the lungs that helps with breathing), the primary cancer site is likely to be in the upper part of the body, such as in the lung or breast.
When cancer is found below the diaphragm, the primary cancer site is likely to be in the lower part of the body, such as the pancreas, liver, or other organ in the abdomen.
Some cancers commonly spread to certain areas of the body. For cancer found in the lymph nodes in the neck, the primary cancer site is likely to be in the head or neck, because head and neck cancers often spread to the lymph nodes in the neck.
The following tests and procedures may be done to find where the cancer first began:
CT scan (CAT scan): A procedure that makes a series of detailed pictures of areas inside the body, such as the chest or abdomen, taken from different angles. The pictures are made by a computer linked to an x-ray machine. A dye may be injected into a vein or swallowed to help the organs or tissues show up more clearly. This procedure is also called computed tomography, computerized tomography, or computerized axial tomography.
MRI (magnetic resonance imaging): A procedure that uses a magnet, radio waves, and a computer to make a series of detailed pictures of areas inside the body. This procedure is also called nuclear magnetic resonance imaging (NMRI).
PET scan (positron emission tomography scan): A procedure to find malignant tumor cells in the body. A small amount of radioactive glucose (sugar) is injected into a vein. The PET scanner rotates around the body and makes a picture of where glucose is being used in the body. Malignant tumor cells show up brighter in the picture because they are more active and take up more glucose than normal cells do.
Endoscopy: A procedure to look at organs and tissues inside the body to check for abnormal areas. An endoscope is inserted through an incision (cut) in the skin or opening in the body, such as the mouth. An endoscope is a thin, tube-like instrument with a light and a lens for viewing. It may also have a tool to remove tissue or lymph node samples, which are checked under a microscope for signs of disease. For example, a colonoscopy may be done.
Tumor marker test: A procedure in which a sample of blood, urine, or tissue is checked to measure the amounts of certain substances made by organs, tissues, or tumor cells in the body. Certain substances are linked to specific types of cancer when found in increased levels in the body. These are called tumor markers. The blood may be checked for the levels of CA-125, CgA, alpha-fetoprotein (AFP), beta human chorionic gonadotropin (β-hCG), or prostate-specific antigen (PSA).