Which tumor marker is elevated in adenocarcinoma but not elevated in mesothelioma?

• A. BRCA-1
• B. BRCA-2
• C. CEA
• D. CYFRA 21-1

Answer: (C)

The trait being tested is how certain serum markers differentiate adenocarcinomas from mesothelioma. Carcinoembryonic antigen (CEA) is a classic marker produced by many glandular (adenocarcinoma) cancers, including lung adenocarcinoma, colorectal cancer, and some others. It is commonly elevated in adenocarcinomas but not typically raised in mesothelioma, whose tumor biology drives different markers.

BRCA-1 and BRCA-2 are genes involved in DNA repair; they are not used as circulating tumor markers to measure tumor burden, so they don’t reflect the presence of an adenocarcinoma versus mesothelioma in a patient.

CYFRA 21-1 is a fragment of cytokeratin-19 and tends to be elevated in several lung cancers, including mesothelioma and non-small cell lung cancer, so it does not provide the distinguishing pattern; it can be elevated in mesothelioma as well as adenocarcinoma, reducing its usefulness for this question.

Thus, the marker that fits the pattern of being elevated in adenocarcinoma but not in mesothelioma is CEA.