Cancer antigen 125

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Related to Cancer antigen 125: Cancer antigen 15-3, Cancer antigen 19-9


any substance capable, under appropriate conditions, of inducing a specific immune response and reacting with the products of that response; that is, with specific antibody or specifically sensitized T lymphocytes, or both. Antigens may be soluble substances, such as toxins and foreign proteins, or particulates, such as bacteria and tissue cells; however, only the portion of the protein or polysaccharide molecule known as the antigenic determinant combines with antibody or a specific receptor on a lymphocyte. Abbreviated Ag. See also immunity. adj., adj antigen´ic.
allogeneic antigen one occurring in some but not all individuals of the same species, e.g., histocompatibility antigens and human blood group antigens; called also isoantigen.
antigen-antibody reaction the reversible binding of antigen to homologous antibody by the formation of weak bonds between antigenic determinants on antigen molecules and antigen binding sites on immunoglobulin molecules.
blood-group a's erythrocyte surface antigens whose antigenic differences determine blood groups.
cancer antigen 125 (CA 125) a glycoprotein antigen found in normal adult tissues such as the epithelium of the fallopian tubes, the endometrium, the endocervix, the pleura, and the peritoneum. Elevated levels are seen in association with epithelial ovarian carcinomas, particularly nonmucinous tumors, as well as with some other malignancies, various benign pelvic disorders, tuberculosis, and cirrhosis.
carcinoembryonic antigen (CEA) an oncofetal glycoprotein antigen originally thought to be specific for adenocarcinoma of the colon, but now known to be found in many other cancers and some nonmalignant conditions. Its primary use is in monitoring the response of patients to cancer treatment.
CD antigen any of a number of cell-surface markers expressed by leukocytes and used to distinguish cell lineages, developmental stages, and functional subsets. Such markers can be identified by specific monoclonal antibodies and are numbered CD1, CD2, CD3, etc. (for cluster designation, according to how their specificity characteristics group together when analyzed by computer).
CD4 antigen an antigen on the surface of helper T cells; the normal range of helper cells is 800 to 1200 per cubic mm of blood. The human immunodeficiency virus binds to this antigen and infects and kills T cells bearing this antigen, thus gradually destroying the body's ability to resist infection. CD4 can be administered in a soluble form to increase the amount of it in the circulation and interfere with the ability of HIV to affect CD4 antigens on the cell.
class I a's major histocompatibility antigens found on virtually every cell, human erythrocytes being the only notable exception; they are the classic histocompatibility antigens recognized during graft rejection.
class II a's major histocompatibility antigens found only on immunocompetent cells, primarily B lymphocytes and macrophages.
conjugated antigen antigen produced by coupling a hapten to a protein carrier molecule through covalent bonds; when it induces immunization, the resultant immune response is directed against both the hapten and the carrier.
cross-reacting antigen
1. one that combines with antibody produced in response to a different but related antigen, owing to similarity of antigenic determinants.
2. identical antigens in two bacterial strains, so that antibody produced against one strain will react with the other.
extractable nuclear a's ENA; protein antigens, not containing DNA, that are extractable from cell nuclei in phosphate-buffered saline; anti-ENA antibodies are a component of the antinuclear antibodies occurring in systemic lupus erythematosus and other connective tissue diseases.
flagellar antigen H antigen.
Forssman antigen a heterogenetic antigen discovered in guinea pig tissues, capable of lysing sheep erythrocytes in the presence of complement. It is found usually in animal organs but occasionally in blood, and induces formation of an antibody (Forssman antibody, a type of heterophile antibody) only when combined with protein or hog serum. Davidsohn's Differential Test was historically used to differentiate between the heterophile sheep agglutinins in human serum that were due to Forssman antigen and those due to infectious mononucleosis; this is based upon the fact that boiled guinea pig kidney will absorb heterophile sheep cell agglutinins produced by Forssman antigen, but not those produced by infectious mononucleosis.
H antigen (Ger. Hauch, film), the antigen that occurs in the flagella of motile bacteria.
hepatitis B core antigen (HBcAg) a core protein antigen of the hepatitis B virus present inside complete virions (Dane particles) and in the nuclei of infected hepatic cells, indicating the presence of reproducing hepatitis B virus. The antigen is not present in the blood of infected individuals, but antibodies against it appear during the acute infection; they do not protect against reinfection.
hepatitis B e antigen (HBeAg) an antigen of hepatitis B virus sometimes present in the blood during acute infection, usually disappearing afterward but sometimes persisting in chronic disease. Anti-HBe antibodies appear transiently during convalescence; they do not protect against reinfection.
hepatitis B surface antigen (HBsAg) one present in the serum of those infected with hepatitis B, consisting of the surface coat lipoprotein of the hepatitis B virus. Tests for serum HbsAg are used in the diagnosis of hepatitis B and in testing blood products for infectivity.
heterogeneic antigen xenogeneic antigen.
heterogenetic antigen (heterophil antigen) (heterophile antigen) one capable of stimulating the production of antibodies that react with tissues from other animals or even plants.
histocompatibility a's genetically determined isoantigens present on the cell membranes of nucleated cells of most tissues, which incite an immune response when grafted onto a genetically disparate individual and thus determine the compatibility of tissues in transplantation. Major histocompatibility antigens are those that belong to the major histocompatibility complex, which in humans contains the hla antigens. Minor histocompatibility antigens are those that can cause delayed tissue rejection.
HLA a's (human leukocyte a's) see hla antigens.
H-Y antigen a minor histocompatibility antigen present in all tissues of normal males and coded for by a structural gene on the short arm of the Y chromosome; it is thought to promote the differentiation of indifferent gonads into testes, thus determining male sex.
isogeneic antigen an antigen carried by an individual which is capable of eliciting an immune response in genetically different individuals of the same species, but not in an individual bearing it.
K antigen a bacterial capsular antigen, a surface antigen external to the cell wall.
lymphogranuloma venereum antigen a sterile suspension of Chlamydia lymphogranulomatis; used as a dermal reactivity indicator.
M antigen a type-specific antigen that appears to be located primarily in the cell wall and is associated with virulence of Streptococcus pyogenes.
mumps skin test antigen a sterile suspension of mumps virus; used as a dermal reactivity indicator.
nuclear a's the components of cell nuclei with which antinuclear antibodies react.
O antigen (Ger. ohne Hauch, without film), the antigen that occurs in the bodies of bacteria.
oncofetal antigen a gene product that is expressed during fetal development, but repressed in specialized tissues of the adult and that is also produced by certain cancers. In the neoplastic transformation, the cells dedifferentiate and these genes can be derepressed so that the embryonic antigens reappear. Examples are alpha-fetoprotein and carcinoembryonic antigen.
organ-specific antigen any antigen that occurs exclusively in a particular organ and serves to distinguish it from other organs. Two types of organ specificity have been proposed: (1) first-order or tissue specificity is attributed to the presence of an antigen characteristic of a particular organ in a single species; (2) second-order organ specificity is attributed to an antigen characteristic of the same organ in many, even unrelated, species.
partial antigen an antigen that does not produce antibody formation, but gives specific precipitation when mixed with the antibacterial immune serum.
pollen antigen the essential polypeptides of the pollen of plants extracted with a suitable menstruum, used in diagnosis, prophylaxis, and desensitization in hay fever.
antigen presentation the presentation of ingested antigens on the surface of macrophages in close proximity to histocompatibility antigens. Some populations of T lymphocytes can only be triggered by antigens that are presented in this way. Thus macrophages play a role in inducing cell-mediated immunity.
private a's antigens of the low-frequency blood groups, so called because they are found only in members of a single kindred.
prostate-specific antigen (prostatic specific antigen) an antigen that is elevated in all patients with prostatic cancer and in some with an inflamed prostate gland.
public a's antigens of the high-frequency blood groups, so called because they are found in many persons.
self antigen an autoantigen, a normal constituent of the body against which antibodies are formed in autoimmune disease.
sequestered a's the cellular constituents of tissue (e.g., the lens of the eye and the thyroid) sequestered anatomically from the lymphoreticular system during embryonic development and thus thought not to be recognized as “self.” Should such tissue be exposed to the lymphoreticular system during adult life, an autoimmune response would be elicited.
somatic a's antigens, usually cell surface antigens, of the body of a bacterial cell, in contrast to flagellar or capsular antigens.
T antigen
1. any of several antigens, coded for by the viral genome, associated with transformation of infected cells by certain DNA tumor viruses. Called also tumor antigen.
2. an antigen present on human erythrocytes that is exposed by treatment with neuraminidase or contact with certain bacteria.
see CD a.
T-dependent antigen one that requires the presence of helper T cells to stimulate antibody production by B cells; most antigens are T-dependent.
T-independent antigen an antigen that can trigger B lymphocytes to produce antibodies without the participation of T lymphocytes. See also T-dependent antigen.
tumor antigen T antigen (def. 1).
tumor-specific antigen (TSA) any cell-surface antigen of a tumor that does not occur on normal cells of the same origin.
V antigen (Vi antigen) an antigen contained in the sheath of a bacterium, as Salmonella typhosa (the typhoid bacillus), and thought to contribute to its virulence.
xenogeneic antigen an antigen common to members of one species but not to members of other species; called also heterogeneic antigen.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

CA 125 (Cancer antigen 125)

A tumor marker associated with ovarian cancer.
Mentioned in: Tumor Markers
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.

Cancer Antigens: CA 15-3, CA 19-9, CA 125, and Carcinoembryonic

Synonym/acronym: Carcinoembryonic antigen (CEA), cancer antigen 125 (CA 125), cancer antigen 15-3 (CA 15-3), cancer antigen 19-9 (CA 19-9), cancer antigen 27.29 (CA 27.29).

Common use

To identify the presence of various cancers, such as breast and ovarian, as well as to evaluate the effectiveness of cancer treatment.


Serum (1 mL) collected in a red-top tube. Care must be taken to use the same assay method if serial measurements are to be taken.

Normal findings

(Method: Electrochemiluminometric immunoassay)
Smoking StatusConventional UnitsSI Units (Conventional Units × 1)
SmokerLess than 5.0 ng/mLLess than 5.0 mcg/L
NonsmokerLess than 2.5 ng/mLLess than 2.5 mcg/L
Conventional UnitsSI Units (Conventional Units × 1)
CA 125
Less than 35 units/mLLess than 35 kU/L
CA 15-3
Less than 25 units/mLLess than 25 kU/L
CA 19-9
Less than 35 units/mLLess than 35 kU/L
CA 27.29
Less than 38.6 units/mLLess than 38.6 kU/L


Carcinoembryonic antigen (CEA) is a family of 36 different glycoproteins whose function is believed to be involved in cell adhesion. These structurally related proteins are part of the immunoglobulin superfamily. CEA is normally produced during fetal development and rapid multiplication of epithelial cells, especially those of the digestive system. A small amount of circulating CEA is detectable in the blood of normal adults; normal half-life is 7 days. The liver is the main site for metabolism of CEA. Because of the variability in CEA molecules the test is not diagnostic for any specific disease and is not useful as a screening test for cancer. However, it is very useful for monitoring response to therapy in breast, liver, colon, and gastrointestinal cancer. Serial monitoring is also a useful indicator of recurrence or metastasis in colon or liver carcinoma. CEA levels are higher in the blood of smokers than in non-smokers so most laboratories will have a normal range for each group.

CA 125 or Muc16 is a glycoprotein member of the mucin family and is present in normal endometrial tissue. It appears in the blood when natural endometrial protective barriers are destroyed, as occurs in cancer or endometriosis. CA 125 is most useful in monitoring the progression or recurrence of known ovarian cancer. It is not useful as a screening test because elevations can occur with numerous other conditions such as endometriosis, other diseases of the ovary, menstruation, pregnancy, and uterine fibroids. Persistently rising levels indicate a poor prognosis. Levels may also rise in pancreatic, liver, colon, breast, and lung cancers. Absence of detectable levels of CA 125 does not rule out the presence of tumor.

CA 15-3 monitors patients for recurrence or metastasis of breast carcinoma.

CA 19-9 is a carbohydrate antigen used for post-therapeutic monitoring of patients with gastrointestinal, pancreatic, liver, and colorectal cancer.

CA 27.29 is a glycoprotein product of the muc-1 gene. It is most useful as a serial monitor for response to therapy or recurrence of breast carcinoma.

This procedure is contraindicated for




  • Determine stage of colorectal cancer and test for recurrence or metastasis
  • Monitor response to treatment of breast and gastrointestinal cancers
  • CA 125

  • Assist in the diagnosis of carcinoma of the cervix and endometrium
  • Assist in the diagnosis of ovarian cancer
  • Monitor response to treatment of ovarian cancer
  • CA 15-3 and CA 27.29

  • Monitor recurrent carcinoma of the breast
  • CA 19-9

  • Monitor effectiveness of therapy
  • Monitor gastrointestinal, head and neck, and gynecological carcinomas
  • Predict recurrence of cholangiocarcinoma
  • Predict recurrence of stomach, pancreatic, colorectal, gallbladder, liver, and urothelial carcinomas

Potential diagnosis

Increased in


  • Benign tumors, including benign breast disease
  • Chronic tobacco smoking
  • Cirrhosis
  • Colorectal, pulmonary, gastric, pancreatic, breast, head and neck, esophageal, ovarian, and prostate cancer
  • Inflammatory bowel disease
  • Pancreatitis
  • Radiation therapy (transient)
  • CA 125

  • Breast, colon, endometrial, liver, lung, ovarian, and pancreatic cancer
  • Endometriosis
  • First-trimester pregnancy
  • Menses
  • Ovarian abscess
  • Pelvic inflammatory disease
  • Peritonitis
  • CA 15-3 and CA 27.29

  • Recurrence of breast carcinoma
  • CA 19-9

  • Gastrointestinal, head and neck, and gynecologic carcinomas
  • Recurrence of stomach, pancreatic, colorectal, gallbladder, liver, and urothelial carcinomas
  • Recurrence of cholangiocarcinoma

Decreased in

    Effective therapy or removal of the tumor

Critical findings


Interfering factors


Nursing Implications and Procedure


  • Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
  • Patient Teaching: Inform the patient this test can assist in monitoring the progress of various types of disease and evaluate response to therapy.
  • Obtain a history of the patients complaints, including a list of known allergens, especially allergies or sensitivities to latex.
  • Obtain a history of the patients gastrointestinal, immune, and reproductive systems, as well as results of previously performed laboratory tests and diagnostic and surgical procedures.
  • Obtain a list of the patients current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values online at DavisPlus).
  • Determine if the patient smokes, because smokers may have false elevations of CEA.
  • Review the procedure with the patient. Inform the patient that specimen collection takes approximately 5 to 10 minutes. Address concerns about pain and explain that there may be some discomfort during the venipuncture.
  • Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
  • Note that there are no food, fluid, or medication restrictions unless by medical direction.


  • Potential complications: N/A
  • Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
  • Instruct the patient to cooperate fully and to follow directions. Direct the patient to breathe normally and to avoid unnecessary movement.
  • Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient, and label the appropriate specimen container with the corresponding patient demographics, initials of the person collecting the specimen, date, and time of collection. Perform a venipuncture.
  • Remove the needle and apply direct pressure with dry gauze to stop bleeding. Observe/assess venipuncture site for bleeding or hematoma formation and secure gauze with adhesive bandage.
  • Promptly transport the specimen to the laboratory for processing and analysis.


  • Inform the patient that a report of the results will be made available to the requesting health-care provider (HCP), who will discuss the results with the patient.
  • Recognize anxiety related to test results, and be supportive of perceived loss of independence and fear of shortened life expectancy. Discuss the implications of abnormal test results on the patients lifestyle. Provide teaching and information regarding the clinical implications of the test results, as appropriate. Educate the patient regarding access to counseling services. Provide contact information, if desired, for the American Cancer Association (
  • Reinforce information given by the patients’ HCP regarding further testing, treatment, or referral to another HCP. Decisions regarding the need for and frequency of breast self-examination, mammography, MRI breast, or other cancer screening procedures should be made after consultation between the patient and HCP. The American Cancer Society (ACS) recommends breast examinations be performed every 3 yr for women between the ages of 20 and 39 yr and annually for women over 40 yr of age; annual mammograms should be performed on women 40 yr and older as long as they are in good health. The ACS also recommends annual MRI testing for women at high risk of developing breast cancer. Genetic testing for inherited mutations (BRCA1 and BRCA2) associated with increased risk of developing breast cancer may be ordered for women at risk. The test is performed on a blood specimen. The most current guidelines for breast cancer screening of the general population as well as of individuals with increased risk are available from the American Cancer Society (, the American College of Obstetricians and Gynecologists (ACOG) (, and the American College of Radiology ( Answer any questions or address any concerns voiced by the patient or family.
  • Decisions regarding the need for and frequency of occult blood testing, colonoscopy, or other cancer screening procedures should be made after consultation between the patient and HCP. The American Cancer Society recommends regular screening for colon cancer, beginning at age 50 yr for individuals without identified risk factors. Their recommendations for frequency of screening: annual for occult blood testing (fecal occult blood testing [FOBT] and fecal immunochemical testing [FIT]); every 5 yr for flexible sigmoidoscopy, double contrast barium enema, and CT colonography; and every 10 yr for colonoscopy. There are both advantages and disadvantages to the screening tests that are available today. Methods to use DNA testing of stool are being investigated and awaiting FDA approval. The DNA test is designed to identify abnormal changes in DNA from the cells in the lining of the colon that are normally shed and excreted in stool. The DNA tests under development would use multiple markers to identify colon cancers with various, abnormal DNA changes and would be able to detect precancerous polyps. The most current guidelines for colon cancer screening of the general population as well as of individuals with increased risk are available from the American Cancer Society (, U.S. Preventive Services Task Force (, and the American College of Gastroenterology (
  • Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patients symptoms and other tests performed.

Related Monographs

  • Related tests include barium enema, biopsy breast, biopsy cervical, biopsy intestinal, biopsy liver, capsule endoscopy, colonoscopy, colposcopy, fecal analysis, HCG, liver and spleen scan, MRI breast, MRI liver, mammogram, stereotactic breast biopsy, proctosigmoidoscopy, radiofrequency ablation liver, US abdomen, US breast, and US liver.
  • Refer to the Gastrointestinal, Immune, and Reproductive systems tables at the end of the book for related tests by body system.
Handbook of Laboratory and Diagnostic Tests, © 2013 Farlex and Partners
References in periodicals archive ?
Molina, "Comparison of serum human epididymis protein 4 with cancer antigen 125 as a tumor marker in patients with malignant and nonmalignant diseases," Clinical Chemistry, vol.
[9] Nonstandard abbreviations: CA125, serum cancer antigen 125; EOC, epithelial ovarian cancer; AFP, [alpha]-fetoprotein; CLRs, C-type lectin receptors; MGL, macrophage galactose-type lectin; DC-SIGN, dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin; NP, nanoparticle; LC, liver cirrhosis; Pla, full-term placentas; OvCa, OVCAR-3 ovarian cancer cell line; MAb, monoclonal antibodies; TRF, time-resolved fluorimetry; OvCa-CA125, CA125 purified from OvCa; Pla-CA125, CA125 from placental extract; LC-CA125, CA125 in ascetic fluid of liver cirrhosis.
Hoffmann et al., "Monoclonal antibodies in the diagnosis and follow-up of ovarian cancer: cancer antigen 125 as tumor marker: a cooperative study of the gynecological tumor marker group (GTMG)," Klinische Wochenschrift, vol.
Abbreviations CD: Crohn's disease CA125: Cancer antigen 125 CRP: C-reactive protein TNF[alpha]: Tumour necrosis factor a CT: Computed tomography.
The serum levels of cancer antigen 125 (CA-125), interleukin 18(IL-18) in the peritoneal fluids and cyclooxygenase-2 (COX-2) mRNA expression levels in the ectopic endometrium were detected in this study.
Objective: To evaluate the sensitivity, specificity, and accuracy of the serum tumor markers cytokeratin 19 fragment (CYFRA 21-1), carcinoembryonic antigen (CEA) and cancer antigen 125 (CA125) in the diagnosis of bone metastases in patients with lung cancer.
Results from the last--the Prostate, Lung, Colorectal, and Ovarian trial, which tested screening with cancer antigen 125 and transvaginal ultrasound--showed that 20 surgeries had to be performed to detect one cancer, and the rate of major complications was 20% among patients who underwent surgery (JAMA 2011;305:2295-303).
Oasmia has used a biomarker, cancer antigen 125 (CA-125), to evaluate the efficacy of the treatment in its Phase III trial with Paclical.
The Risk of Ovarian Malignancy Algorithm (ROMA) stratifies women as being at high or low risk for epithelial ovarian cancer based on menopausal stares and preoperative serum levels of two biomarkers: human epididymis protein 4 (HE4) and cancer antigen 125 (CA 125).
In multiple regression with all 29 available personal, lifestyle, and internal exposure parameters, blood lead levels showed a positive association with serum levels of anti-p53, carcino-embryonic antigen (CEA), and tissue polypeptide-specific antigen (TPS) and with an index for mean TAP level ([I.sub.tap]); dioxin-like activity in serum and serum copper showed a positive association with serum CA 125 (cancer antigen 125); and serum zinc showed a positive association with serum levels of c-erbB-2 ectodomain and TPS.
Those found in the blood include PSA (prostate-specific antigen), for prostate cancer in men, and CA 125 (cancer antigen 125), for ovarian cancer in women.