Expressed by fetal liver and the endoderm of the yolk sac, this antigen is present in yolk sac (endodermal sinus) tumours of testis and ovary and a high proportion of other germ cell tumours. However, the staining in yolk sac tumours may be limited and sensitivity is low. Alpha-fetoprotein may also be secreted by other types of tumour, including gastric carcinoma.
Hepatocellular carcinoma. AFP has a low sensitivity, but may be useful in poorly differentiated tumours which are more often positive for AFP but may lack the specific canalicular pattern with p-CEA and CD10. Its specificity is high. It should be used with other antisera.
Hepatoid tumour has a similar immunophenotype to hepatocellular carcinoma. This tumour has been described in the female genital tract (ovary), urinary bladder, lung, gastrointestinal tract (stomach, colon, pancreas, gallbladder), breast and thymus: it represents true hepatocellular differentiation. However, the sensitivity of alpha-fetoprotein in hepatoid tumour, as in hepatocellular carcinoma, is low.
Testicular and ovarian germ cell tumours
References
©SMUHT/PW Bishop