Stains & CD markers
CA 19-9

Last author update: 1 August 2018
Last staff update: 23 June 2021

Copyright: 2018-2023,, Inc.

PubMed Search: CA 19-9 stain

Nat Pernick, M.D.
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Cite this page: Pernick N. CA 19-9. website. Accessed November 29th, 2023.
Definition / general
  • Modified Lewis(a) blood group antigen secreted by or expressed on the surface of cancer cells
  • Used primarily as a serum tumor marker to screen for pancreatic cancer and to monitor effectiveness of therapy
  • However, only 50 - 75% sensitive for initial screening of pancreatic cancer and relatively nonspecific
  • Carbohydrate Antigen 19-9
Prognostic factors
Clinical features
  • Used primarily as a serum biomarker
    • As a serum screening test for pancreatic cancer, is more sensitive than CEA but less sensitive than CXCL8 (Pol Arch Intern Med 2018 Jul 27 [Epub ahead of print])
    • Used to screen for pancreatic cancer but has limited sensitivity and specificity
    • May also be elevated in patients with cholangiocarcinoma or colon cancer
    • Serum levels also elevated in cirrhosis, cholestasis and pancreatitis but values are usually below 1,000 U/mL.
    • Note: individuals that are Lewis negative (5 - 7% of population) do not express CA 19-9 due to the lack of the enzyme fucosyltransferase needed for CA 19-9 production; as a result, a low or undetectable serum CA 19-9 concentration is not informative regarding cancer recurrence (Mayo Clinic: CA19 [Accessed 10 September 2018])
  • Medullary thyroid carcinoma:
  • Lung adenocarcinoma associated malignant pleural effusions:
    • Highly specific (98%) to differentiate from benign effusions but only 55% sensitive (Pathology 2015;47:123)
Microscopic (histologic) images

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Medullary thyroid cancer

Positive staining - normal
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