The cancer of unknown primary is when cells proliferate out of control, cancer develops. Cancerous cells can arise in almost any portion of the body and spread to other parts. Cancers frequently spread from their initial site (where cancer began) to one or more metastatic locations (other parts of the body). Cancers are named after their original site, regardless of where they disseminate throughout the body. Lung cancer that spreads to the liver, for example, is still categorized as lung cancer rather than liver cancer.
It’s not always easy to pinpoint where cancer began. Cancer of unknown primary (CUP) or occult primary cancer occurs when cancer is discovered in one or more metastatic sites but the source site cannot be recognized. This occurs in just a small percentage of malignancies.
Cancer of unknown primary (CUP) is a type of cancer that has spread from another place of the body. According to the American Cancer Society, 2 to 5% of all cancer patients have metastatic tumors for which conventional diagnostics cannot pinpoint the origin of the disease. Cancer of unknown primary origin, also known as occult primary cancer, is most usually seen in the bones, lungs, liver, skin, and lymph nodes.
If the original tumor is too small to be detected with imaging tests, or if the disease has spread to other places of the body and it is uncertain which is the primary site, a person may be diagnosed with cancer of unknown primary.
Additional tests may reveal the primary site of some of these tumors in the future. When this happens, they are no longer classified as cancers of uncertain primary origin and are renamed and treated as cancers of known primary origin.
A swollen lymph node on the side of a person’s neck, for example. Cancer is discovered when it is removed. However, under a microscope, it does not appear to be cancer that usually begins in lymph nodes. It’s possible that it’s a malignancy of unknown origin at this time. The way cancer appears under a microscope could indicate that it started in the mouth, throat, or voice box (larynx). A tiny carcinoma of the larynx may be discovered when this area is investigated. The patient is now diagnosed with laryngeal cancer rather than a cancer of undetermined origin and will be treated accordingly.
In many situations, cancer’s cause is never discovered. Even the most extensive search may not uncover the source site. Even when autopsies are performed on persons who have died of cancer of unknown origin, doctors are frequently unable to locate the spot where cancer began.
The major objective for looking for a cancer of unknown primary’s primary site is to help with treatment. Knowing where cancer started advises the doctor what types of treatments to use because cancer that starts in one location needs the same treatments as it spreads. This is especially significant for tumors that respond well to certain types of chemotherapy or hormone therapy. When the types of cancer that respond best to treatment have been ruled out by tests, determining the exact origin or cancer type becomes less crucial.
Treatment can still be successful even if the primary site is unknown. The appearance of cancer cells under a microscope, the findings of lab tests, and information about which organs it has already impacted can all help doctors forecast which treatments will be most effective.