Cancer of unknown primary origin
Encyclopedia
Cancer of unknown primary origin (CUP) is the diagnosis when metastatic cancer is found but the place where the cancer
began (the primary site) cannot be determined. About two to four percent of all cancer patients have a cancer whose primary site is never identified. Treatment for CUP depends on many factors, including where the metastatic cancer is found, what the cancer cells look like under a microscope, and the patient’s age and general health. Recent advances in diagnostic techniques have improved doctors' abilities to find the primary sites, even when the original diagnoses are "CUP."
can begin in any organ or tissue of the body. The primary, or original, tumor
is usually named for the part of the body or the type of tissue in which the cancer begins. The disease can spread (metastasize) from the primary tumor and form metastatic tumors in other parts of the body. For example, breast cancer cells can metastasize to the lungs and cause the growth of a new tumor. When this happens, the tumor in the lung is called metastatic breast cancer because it is composed of breast cancer cells, not lung cancer cells.
Each year in the United States, several thousand people are diagnosed with metastatic cancer whose primary cancer site is not known. When the primary site cannot be identified, this disease may be called carcinoma of unknown primary (CUP). Most often, the metastatic cancer is first found in the lymph nodes, liver, lung, or bone.
Most patients with an unidentified primary tumor have a cell type called adenocarcinoma
. The term adenocarcinoma refers to cancer that begins in the cells in glandular structures in the lining or covering of certain organs in the body. Common primary sites for adenocarcinomas include the lung, pancreas, breast, prostate, stomach, liver, and colon.
When the cancer cells are poorly differentiated (that is, they look less evolved than normal cells when viewed under a microscope), the cancer may be either a lymphoma or a germ cell tumor
. Lymphomas begin in the lymphatic system
. Germ cell tumors usually begin in the ovaries and testes.
In patients in whom the primary cancer is eventually found, the lung and pancreas are the most common primary cancer sites. CUP also may be traced to the breast, prostate, colon, or rectum as the primary site.
Sometimes, however, even when doctors use very sophisticated methods to try to identify the primary site, the part of the body the cancer cells came from cannot be determined. About 2 to 4 percent of all cancer patients have a cancer whose primary site is never found.
Identifying the primary tumor site is important because knowing its location and type often helps doctors plan the best treatment. Treatment that is specific to the suspected type of cancer is likely to be more effective. Still, when diagnostic tests have not identified the primary site, doctors must decide whether the potential benefits of more extensive testing outweigh a patient’s discomfort and the financial costs.
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
began (the primary site) cannot be determined. About two to four percent of all cancer patients have a cancer whose primary site is never identified. Treatment for CUP depends on many factors, including where the metastatic cancer is found, what the cancer cells look like under a microscope, and the patient’s age and general health. Recent advances in diagnostic techniques have improved doctors' abilities to find the primary sites, even when the original diagnoses are "CUP."
Introduction
CancerCancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
can begin in any organ or tissue of the body. The primary, or original, tumor
Tumor
A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...
is usually named for the part of the body or the type of tissue in which the cancer begins. The disease can spread (metastasize) from the primary tumor and form metastatic tumors in other parts of the body. For example, breast cancer cells can metastasize to the lungs and cause the growth of a new tumor. When this happens, the tumor in the lung is called metastatic breast cancer because it is composed of breast cancer cells, not lung cancer cells.
Each year in the United States, several thousand people are diagnosed with metastatic cancer whose primary cancer site is not known. When the primary site cannot be identified, this disease may be called carcinoma of unknown primary (CUP). Most often, the metastatic cancer is first found in the lymph nodes, liver, lung, or bone.
Identification of the primary tumor
In recent years, microscopic and other diagnostic techniques have improved dramatically. For this reason, doctors can now determine the primary site in about four out of five cases first diagnosed as CUP. 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. Doctors also have other clues that help them find the primary site:- The pattern of spread may suggest the location of the primary site. When the metastatic cancer is found in the upper part of the body, the original site is likely to be above the diaphragmThoracic diaphragmIn the anatomy of mammals, the thoracic diaphragm, or simply the diaphragm , is a sheet of internal skeletal muscle that extends across the bottom of the rib cage. The diaphragm separates the thoracic cavity from the abdominal cavity and performs an important function in respiration...
at sites such as the lung and breast. If the metastatic cancer appears first in the lower part of the body, the primary cancer is likely to be at sites below the diaphragm, such as the pancreas and liver.
- The type of cell found in the metastatic cancer can also provide clues about the hidden primary site.
Most patients with an unidentified primary tumor have a cell type called adenocarcinoma
Adenocarcinoma
Adenocarcinoma is a cancer of an epithelium that originates in glandular tissue. Epithelial tissue includes, but is not limited to, the surface layer of skin, glands and a variety of other tissue that lines the cavities and organs of the body. Epithelium can be derived embryologically from...
. The term adenocarcinoma refers to cancer that begins in the cells in glandular structures in the lining or covering of certain organs in the body. Common primary sites for adenocarcinomas include the lung, pancreas, breast, prostate, stomach, liver, and colon.
When the cancer cells are poorly differentiated (that is, they look less evolved than normal cells when viewed under a microscope), the cancer may be either a lymphoma or a germ cell tumor
Germ cell tumor
A germ cell tumor is a neoplasm derived from germ cells. Germ cell tumors can be cancerous or non-cancerous tumors. Germ cells normally occur inside the gonads...
. Lymphomas begin in the lymphatic system
Lymphatic system
The lymphoid system is the part of the immune system comprising a network of conduits called lymphatic vessels that carry a clear fluid called lymph unidirectionally toward the heart. Lymphoid tissue is found in many organs, particularly the lymph nodes, and in the lymphoid follicles associated...
. Germ cell tumors usually begin in the ovaries and testes.
In patients in whom the primary cancer is eventually found, the lung and pancreas are the most common primary cancer sites. CUP also may be traced to the breast, prostate, colon, or rectum as the primary site.
Sometimes, however, even when doctors use very sophisticated methods to try to identify the primary site, the part of the body the cancer cells came from cannot be determined. About 2 to 4 percent of all cancer patients have a cancer whose primary site is never found.
Identifying the primary tumor site is important because knowing its location and type often helps doctors plan the best treatment. Treatment that is specific to the suspected type of cancer is likely to be more effective. Still, when diagnostic tests have not identified the primary site, doctors must decide whether the potential benefits of more extensive testing outweigh a patient’s discomfort and the financial costs.
Treatment
CUP is a term that refers to many different cancers. For that reason, treatment depends on where the cancer is found, what the cancer cells look like under a microscope, and the patient’s age and overall physical condition. No method is standard, but chemotherapy, radiation therapy, hormone therapy, and surgery may be used alone or in combination to treat patients who have CUP. Even when the cancer is unlikely to be cured, treatment may help the patient live longer or improve the patient’s quality of life. However, the potential side effects of the treatment must be considered along with the potential benefits.Sources
- NCI: Cancer of Unknown Primary Origin (public domain)
External links
- Clinically reviewed information on unknown primary cancer for patients, from Cancer Research UKCancer Research UKCancer Research UK is a cancer research and awareness charity in the United Kingdom, formed on 4 February 2002 by the merger of The Cancer Research Campaign and the Imperial Cancer Research Fund. Its aim is to reduce the number of deaths from cancer. As the world's largest independent cancer...
- http://www.cancerhelp.org.uk/type/unknown-primary-cancer/