Which tumor marker is associated with Lewis antigen status?

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Multiple Choice

Which tumor marker is associated with Lewis antigen status?

Explanation:
CA 19-9 is tied to the Lewis antigen system because it is the sialyl-Lewis A carbohydrate determinant on mucins. Its presence depends on the Lewis antigen Le^a (and the FUT3 enzyme that builds it). In individuals who are Lewis antigen negative (Le^a−Le^b−), this marker cannot be produced, so CA 19-9 may be undetectable even when a tumor is present. That connection to Le^a status is why CA 19-9 is associated with Lewis antigen status. The other markers—CA 125, CA 15-3, and CEA—are not dependent on Lewis antigens and are influenced by a broader range of conditions.

CA 19-9 is tied to the Lewis antigen system because it is the sialyl-Lewis A carbohydrate determinant on mucins. Its presence depends on the Lewis antigen Le^a (and the FUT3 enzyme that builds it). In individuals who are Lewis antigen negative (Le^a−Le^b−), this marker cannot be produced, so CA 19-9 may be undetectable even when a tumor is present. That connection to Le^a status is why CA 19-9 is associated with Lewis antigen status. The other markers—CA 125, CA 15-3, and CEA—are not dependent on Lewis antigens and are influenced by a broader range of conditions.

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