http://www.quality-assurance-solutions.com/quality-assurance-metrics.html 

http://www.liversociety.org/html/tumor_markers.html

This link may help

Alpha-Fetoprotein

Alpha-fetoprotein (AFP) is normally produced by a developing fetus. AFP levels begin to decrease soon after birth and are usually undetectable in the blood of healthy adults (except during pregnancy). An elevated level of AFP strongly suggests the presence of either primary liver cancer or germ cell cancer (cancer that begins in the cells that give rise to eggs or sperm) of the ovary or testicle. Only rarely do patients with other types of cancer (such as stomach cancer) have elevated levels of AFP. Noncancerous conditions that can cause elevated AFP levels include benign liver conditions, such as cirrhosis or hepatitis; ataxia 

Good question. 

Can some one please explain what "tumor markers" are and what the range means? THX !