Immunofluo rescent demonstration of alpha‐fetoprotein and other plasma proteins in yolk sac tumor

All seven pure yolk sac tumors of gonadal and extragonadal origin tested showed a bright positive fluorescence for alpha‐fetoprotein in the tumor tissue. A positive reaction was seen in both the tumor cells and the hyaline globules. In all cases, however, the positive fluorescence was distributed in some focal areas of the tumor tissue. Certain tumor cells showed a strong granular intracytoplasmic fluorescence, whereas others showed a weak or a negative fluorescence. The fluorescence‐positive tumor cells were located mainly in the areas rich in fluorescence‐positive hyaline globules. Besides alpha‐fetoprotein, certain plasma proteins–‐albumin, alpha‐1 antitrypsin, and transferrin–‐were also demonstrated in all five yolk sac tumors tested. The pattern of the distribution of positive fluorescence was basically similar to that of alpha‐fetoprotein. Other plasma proteins–‐orosomucoid, haptoglobin, Gc‐globulin, alpha‐2 macro‐globulin, hemopexin, and ceruloplasmin–‐were present in certain tumors, and were distributed mainly in a limited number of hyaline globules. Both igG and IgA were present in two tumors of ovarian origin. The immunoglobulins were for the most part present in extracellular hyaline globules, suggesting that these are taken up from the circulation. Test for fibrinogen, beta‐lipoprotein, IgM, IgE, beta‐1C/beta‐1A and beta‐1E globulins were negative or questionable. In a hepatoblastoma, tests for alpha‐fetoprotein were positive, but those for other plasma proteins were negative. Fine granular fluorescence was seen in each hepatocellular tumor cell. Mesenchymal elements were virtually unstained.