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CA-125 (Cancer Antigen 125)

Analyte: Cancer Antigen 125

Specimen Type: For information on this assay, please contact PBI.

Biological or Clinical Significance:

CA 125 belongs to the family of hybridoma-defined tumor markers. The antigenic determinant CA 125 has a protein structure with associated carbohydrate side-chains.

CA 125 is found in a high percentage of non-mucinous ovarian tumors of epithelial origin and can be detected in serum. It does not occur on the surface epithelium of normal ovaries (adult and fetal). Ovarian carcinoma accounts for about 20% of gynecological tumors; the incidence is 15/100,000. In addition, CA 125 has been found in the amniotic fluid and in the coelomic epithelium; both of these tissues are of fetal origin. In tissues of adult origin, the presence of CA 125 has been demonstrated in the epithelium of the oviduct, in the endometrium and in the endocervix.

Elevated values are sometimes found in various benign gynecological diseases such as ovarian cysts, ovarian metaplasia, endometriosis, uterus myomatosus or cervicitis. Slight elevations of this marker may also occur in early pregnancy and in various benign diseases (e.g. acute and chronic pancreatitis, benign gastrointestinal diseases, renal insufficiency, autoimmune diseases and others). Markedly elevated levels have been found in benign liver diseases such as cirrhosis and hepatitis. Extreme elevations can occur in any kind of ascites due to malignant and benign diseases. Although the highest CA 125 values occur in patients suffering from ovarian carcinoma, clearly elevated values are also observed in malignancies of the endometrium, breast, gastrointestinal tract, and various other malignancies. Although CA 125 is a relatively unspecific marker, it is today the most important tumor marker for monitoring the therapy and progress of patients with serous ovarian carcinoma. At primary diagnosis the sensitivity of CA 125 depends on the FIGO stage (FIGO = Federation of Gynecology and Obstetrics); higher tumor stages are associated with higher CA 125 levels.

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