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The signs and symptoms of a cancer of unknown primary vary depending on which organs it has spread to. It’s important to note that none of the symptoms listed below is caused only by CUP. In fact, they are more likely to be caused by something other than cancer. Still, if you have symptoms that suggest that something abnormal may be going on, see a doctor so that the cause can be evaluated and treated, if needed.
Some possible symptoms of CUP include:
Normal lymph nodes are bean-sized collections of immune system cells located throughout the body that are important in fighting infections. Cancers often spread to the lymph nodes, which become swollen and firmer. A person might notice a lump (enlarged lymph node) under the skin on the side of the neck, above the collarbone, under the arms, or in the groin area. Sometimes, a doctor notices them first during a routine checkup.
A mass is an abnormal area such as a swelling or firm area that can be caused by a tumor. This can be caused by cancer growing in the liver or less often, the spleen.
Sometimes the cancer cells grow on the surface of many organs in the abdomen. This may cause ascites, the buildup of fluid inside the abdomen. The fluid buildup can swell the abdomen. It can sometimes lead to a feeling of fullness or bloating.
This symptom may be caused by cancer that has spread to the lungs or by the build-up of fluid and cancer cells in the space around the lungs (a pleural effusion).
This may be caused by cancer growing around nerves or by tumors pressing against internal organs.
Cancer that has spread to the bones can sometimes cause severe pain. Common areas of pain include the back and the legs and hips, but any bone can be affected. The bones may be weakened by the cancer’s spread, and can break from minor injuries or even the normal stress of supporting the body’s weight. This can lead to a sudden severe pain or worsening of pain that was already there.
Some cancers that start in internal organs can spread through the bloodstream to the skin. Because bumps in the skin are easily seen, skin metastases are sometimes the first sign of spread from a CUP.
Cancer that started in the gastrointestinal system (such as esophagus, stomach, small intestines, or colon) can bleed. Often this occurs at a slow rate, so that the blood isn’t visible in the stool. Eventually, this can lead to low red blood cell counts.
Red blood cell counts can also become low if the cancer spreads to the bone marrow and crowds out the normal blood forming cells.
These symptoms are often seen with more advanced cancers. They may occur because the cancer has spread to specific organs or systems such as the bone marrow or digestive system. Some cancers also release substances into the bloodstream that can affect metabolism and cause these problems.
This is by no means a complete list of symptoms that might be caused by CUPs. Again, most of the symptoms above are more likely to be caused by conditions other than cancer, Still, if you have any of these problems, it’s important to see your doctor right away so the cause can be found and treated, if needed.
The American Cancer Society medical and editorial content team
Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.
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Søndergaard D, Nielsen S, Pedersen CNS, Besenbacher S. Prediction of primary tumors in cancers of unknown primary. J Integr Bioinform. 2017 Jul;14(2):pii. doi: 10.1515/jib-2017-0013.
National Cancer Institute. Physician Data Query (PDQ). Cancer of Unknown Primary Treatment. 07/25/2015. Accessed at: https://www.cancer.gov/types/unknown-primary/hp/unknown-primary-treatment-pdq on February 9, 2018.
Tomuleasa C, Zaharie F, Muresan MS, Pop L, Fekete Z, Dima D, Frinc I, Trifa A, Berce C, Jurj A, Berindan-Neagoe I, Zdrenghea M. How to diagnose and treat a cancer of unknown primary site. J Gastrointestin Liver Dis. 2017 Mar;26(1):69-79. doi: 10.15403/jgld.2014.1121.261.haz.
Varadhachary GR, Lenzi R, Raber MN, Abbruzzese JL. Carcinoma of Unknown Primary In: Neiderhuber JE, Armitage JO, Doroshow JH, Kastan MB, Tepper JE, eds. Abeloff’s Clinical Oncology. 5th ed. Philadelphia, PA. Elsevier: 2014:1792-1803.
Last Revised: March 9, 2018
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