Which of the following enzymes is commonly used as a tumor marker?

• A. LD
• B. Lipase
• C. Aldolase
• D. Catalase

Answer: (A)

Lactate dehydrogenase is commonly used as a tumor marker because many cancers release this enzyme into the bloodstream as tumor cells turn over and die, leading to elevated levels that can reflect disease burden and help monitor treatment response. It’s not specific to one cancer, but it’s a useful, general indicator across various malignancies. The other enzymes listed are not standard tumor markers: lipase points more to pancreatic or biliary disease, aldolase is mainly a muscle-related marker, and catalase has no established role as a tumor marker.