[General concepts of alpha-fetoprotein (AFP)-secreting tumors, with special reference to the histogenesis]

Recently, in addition to yolk sac tumors (YST) and hepatocellular carcinomas, many AFP-secreting tumors have been reported. A comparative morphological study of YST to the human yolk sac has revealed tumor cells mimicking the behavior of the human yolk sac endodermal cells (HYSEC). Another investigation suggests that an embryonal carcinoma (adult type), a gastric adenocarcinoma, or an ovarian adenocarcinoma, each showing no histologic features specific for YST, have a selective differentiation to HYSEC which can secrete an increased serum AFP. These tumors might well be called endodermal cell tumors. The histogenesis of AFP-secreting tumors can be attributed to the endodermal origin (or retrodifferentiation to the HYSEC).