Expression of human chorionic gonadotropin in testicular germ cell tumors

Background: We have shown that most patients with seminomas have elevated serum concentrations of the free β subunit of human chorionic gonadotropin (hCGβ) and that in nonseminomatous testicular cancer, most of the hCG in the serum is hyperglycosylated (hCG-h). However, the tissue expression of hCG-h or hCGβ in germ cell tumors (GCTs) has not been reported. Our objective was to study the expression and diagnostic value of hCG-h and hCGβ in testicular GCTs.

Methods: We studied the immunohistochemical expression of hCG, hCG-h, hCGβ, and the free α subunit of hCG (hCGα) in GCTs from 154 patients. We compared the tissue expression with serum concentrations and evaluated the correlation between staining intensity, established prognostic variables, and outcome.

Results: The expression varied between tumor types. All forms of hCG, including hCG-h, were detected in embryonal carcinomas (22%) and mixed GCTs (48%). Polyclonal hCG and monoclonal hCGβ antibodies detected immunoreactivity in some seminomas (7%). No form of hCG was found in spermatocytic seminomas, pure teratomas, or a yolk sac tumor. The serum concentrations correlated with the corresponding tumor expression. The staining intensities of hCG, hCGβ, hCG-h, and hCGα correlated with disease stage but not significantly with relapse, disease-related mortality, or progression-free survival.

Conclusion: Trophoblastic tissue expresses hCG, hCG-h, and free subunits together whereas seminoma tissue occasionally expresses hCGβ. This difference might aid in differential diagnosis of some difficult-to-classify cases.