Substances such as enzymes, antigens, and hormones present in the circulation that can be used for cancer screening, to confirm a diagnosis, or to monitor the clinical course of a malignancy are called:

Analytes.

Explanation:

An analyte is a substance/bio-molecule which is being analyzed with the help of a laboratory procedure or test.  

In case of cancer, the cancerous cells produce different analytes (enzymes or antigens or hormones) than the normal cells do. So if we detect a different analyte than the normal analyte then we can easily infer that the person being analyzed has cancer.  

b is dominant over the allele for the white fur.

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