Detection of human chorionic gonadotropin in fresh and formalin-fixed testicular tumor tissue. Comparison of sensitivity of immunoperoxidase to radioimmunoassay

Abstract

Immunmocytochemical techniques for the detection of human chorionic gonadotropin (HCG), such as immunoperoxidase or immunofluorescence, allow detection but not quantification of this hormone. A modification of standard radioimmunoassay (RIA) techniques allows utilization of tissue slurries and yields quantitative data on tissue HCG levels. Tissue slurry RIAs and indirect immunoperoxidase were performed on fresh and formalin-fixed tissue specimens from 15 patients with nonseminomatous testicular tumors. HCG detectability by RIA or immunoperoxidase was markedly decreased by formalin fixation. Tissue specimens with high levels of HCG in the fresh state yielded positive immunoperoxidase and RIA results, while specimens with minimally elevated HCG levels tended to be negative. Results of tissue slurry RIAs correlated well with immunoperoxidase results. The detection of HCG in fixed tissue appears to underestimate the amount of HCG present in fresh specimens. Therefore, a negative RIA on formalin-fixed tissue slurry or negative immunoperoxidase of the formalin-fixed, paraffin-embedded tissue does not rule out the absence of HCG in fresh tissue.