Morphometric, immunohistochemical, and electron-microscopic studies were undertaken in an attempt to identify the types of
hepatoblastoma cellular elements responsible for the synthesis of
alpha-fetoprotein (AFP), and to see how they may relate to serum AFP levels and the metastatic spread and prognosis of the
hepatoblastoma. Morphometric studies of 21
hepatoblastomas with statistical treatment of the results revealed a moderately strong reliable correlation of the AFP serum titer with the volume ratio of embryonal
tumor cells and with that of those
tumor elements of endodermal hepatic
diverticulum which are similar to the latter cells with regard to degree of differentiation. Also, a consistent, reliable negative correlation was demonstrated between serum AFP titer and the volume of fetal
hepatoblastoma cells. The volume ratio of stromal elements was found to be subject to chance variations and not to correlate with serum AFP level. Immunohistochemical and electron-microscopic studies confirmed the morphometric findings and showed AFP synthesis to be effected by poorly differentiated
hepatoblastoma cells--by endodermal hepatic
diverticulum elements at first and by embryonal and intermediate
tumor cells later--and to decrease as the liver
tumor cells differentiate further. It is concluded that a high serum AFP level is, generally, an indication that the
hepatoblastoma is an extensive one and consists of poorly differentiated cells so that the prognosis is unfavorable.