alpha fetoprotein tumor marker liverliver cancer alpha fetoprotein levelsserum alpha fetoprotein liver canceralpha fetoprotein tumoralpha fetoprotein markerfetoprotein tumor markeralpha 1 fetoproteinalpha feto tumor markeralpha fetoprotein cirrhosishigh alpha fetoprotein in pregnancyabnormal alpha fetoproteinalpha fetoprotein liver