Immunohistochemical demonstration of hemoglobin F (HbF) in testicular germ cell tumors.

Increased serum levels of fetal hemoglobin (HbF) in patients with testicular malignancy have been suggested to be due to reactivation of HbF synthesis in the bone marrow. Since HbF is known to be present in the normal yolk sac, a series of 12 testicular germ cell tumors containing yolk sac tumor (YST) components and/or embryonal carcinoma (EC) were examined by the indirect immunoperoxidase technique for the presence of HbF in the tumor tissue. In nine tumors, the YST components, i.e., cells of the microcystic and reticular patterns as well as of endodermal appearance, were positively stained. In addition, groups of positively stained cells were found in the mesenchymal stroma of the tumors. In seven tumors, varied numbers of EC tumor cells were also HbF-positive. In the vessels positively stained, blood cells occurred to a variable extent. The appearance and distribution of HbF-positive cells in the YST components are in accordance with the various types of blood-forming cells hitherto accepted to be present in the normal conceptus during development. In addition, the staining results indicate that YST imitates not only the yolk sac proper, but also other fetal structures. Furthermore, the results support the suggestion, that the HbF in the peripheral blood of patients with testicular tumors may originate in the tumor tissue, and not necessarily in the bone marrow. Evaluation of HbF as a serologic tumor marker in such patients is, therefore, recommended.