Cancer of unknown primary origin
A diagnosis of CUP requires a clinical picture consistent with metastatic disease and one or more biopsy results inconsistent with a tumor cancer.
Rarely (3–5% of the time), the primary tumor cannot be found because it is too small, or because it has regressed due to immune system activity or other factors.
CUP usually comes to attention because of masses or swellings found somewhere in the body, either by physical examination or on medical imaging performed for another indication.
Because the site of the primary tumor usually dictates the treatment and expected outcome, this view may help create uncertainty and anxiety among health professionals and patients, who may feel that their evaluation has been incomplete.
After a detailed imaging and pathologic analysis, oncologists can tell their patients with CUP that metastasis does not always involve the formation of a primary tumor, and that their diagnostic evaluation is complete.
Additional clues which may be helpful in determining the primary site include the pattern of spread, and the cell type, which is based on its appearance under a microscope (histology).
[8] The initial work-up of a cancer of unknown primary includes a CT scan of the chest, abdomen, and pelvis, with IV contrast.
[7] Women with enlarged lymph nodes (lymphadenopathy) confined to the axillary region with CUP should have a mammogram or ultrasound to evaluate for possible breast cancer.
[medical citation needed] 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.
Identifying the primary tumor site is important because knowing its location and type often helps doctors plan the best treatment.
[medical citation needed] Antibodies may be used to determine the expression of protein markers on the surface of cancer cells.
Individual tests often do not provide definitive answers, but sometimes patterns may be observed, suggesting a particular site of origin (e.g. lung, colon, etc.).
[7] However, there is a lack of definitive research data showing that treatment guided by information from immunohistochemical testing improves outcomes or long-term prognosis.
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.
[medical citation needed] The remaining 10 percent are either poorly or undifferentiated malignant neoplasms (5%), or squamous cell carcinomas (5%).
[7] Survival rates are higher when the cancer is more limited to lymph nodes, pleura, or peritoneal metastasis, which ranges from 14 to 16 months.
