When a doctor diagnoses a patient with cancer, he or she can typically identify from which organ the cancer originated, even after the malignant cells have metastasized and spread to other organs. In a few cases, the doctor will discover a cancerous tumor whose genetic profile does not match that of the affected organ. If the doctor or oncologist cannot match the genetic origin of the cancer to a particular body tissue, the disease gets labeled a “Cancer of Unknown Primary Origin” (CUP).
CUP is the diagnosis doctors employ for a metastasized cancer that has moved from its original site to other organs throughout the body. In many instances, further testing reveals the origin site and the diagnosis will change from CUP to a cancer of the originating site. For example, a patient may develop a CUP of the lymph nodes near the throat, but later testing will reveal the disease to be a form of laryngeal cancer.
Types of CUP
The type of cancer cells found in a CUP tumor may reveal clues as to the origin site.
* Adenocarcinoma is a cancer of the glands, such as the adrenal and reproductive glands. Adenocarcinoma is the most common form of CUP.
* Poorly differentiated carcinoma is a form of cancer where the cells have a remarkably different structure than the surrounding healthy tissue.
* Squamous cell cancer is typically found in the linings of organs. The flat structure of the surrounding cells can make squamous cell cancers difficult to trace.
Today, with advances in diagnostic imaging and a better understanding of how cancer cells operate, up to eighty percent of all cancer cases receive an initial diagnosis that includes the organ where the cancer started. Even after an initial review, most CUP diagnoses are revised to reflect the originating site. Still, as many as four percent of all cancer cases will carry the diagnosis of CUP.
Symptoms and Diagnosis of CUP
Sometimes symptoms of CUP include a swelling of the lymph nodes (found in the armpit, near the collarbone or inside the upper thigh), poor appetite and energy, skin lesions and pain in the bones. However, CUP does not have any unique symptoms that separate it from other forms of cancer.
Doctors use all the tools of the trade, from microscopes to MRI scans, to determine the type of cancer that may be possible in a CUP diagnosis. They may examine the cancer cells through passive imaging scans (X-rays, CAT scans, MRI scans) or obtain cell samples through more invasive procedures (blood test, biopsy surgery, endoscopy).
Treating CUP
When a doctor or oncologist cannot determine the origin site of the cancer, they will often recommend a wide range of treatments in order to cover as many potential scenarios as possible. A treatment regimen for a CUP patient may include surgery to remove portions of the tumor, radiation therapy to destroy the cancer cell’s genetic structure, and chemotherapy to inhibit the further growth and metastasis of the tumor.
Prognosis for CUP Patients
As with any form of cancer, early diagnosis and treatment are the keys to a good prognosis. Other factors, such as age, physical fitness, family history and the rate of tumor growth also enter into a patient’s chances of survival. Doctors will take all of these factors into account, combined with the data on the cancer from the diagnostic tests, to determine the patient’s prognosis.
Patients with a diagnosis of CUP probably want to ask their doctor many of the same questions as other cancer patients, such as the length of time required for surgery and side effects of treatments. CUP patients should also ask about the tests involved in determining the primary origin. If the pain or expense of undergoing such tests will not directly contribute to improving the patient’s chances for recovery, then they may want to reconsider.
CUP is becoming an increasingly rare diagnosis. As the knowledge base for cancer increases, so does the doctor’s ability to diagnose and trace most forms of the disease.
Sources of information on this page: National Cancer Institute, American Cancer Society, CancerHelpUK
