5H4-E2 reacts with hCG beta chain, which is specific for hCG. The alpha chain is identical among hCG, TSH, FSH and LH. While hCG is secreted in large quantities by normal trophoblasts, it is present only in trace amounts in non-pregnant urine and sera but rises sharply during pregnancy. Besides trophoblastic tumors e.g. choriocarcinoma, large cell carcinoma, adenocarcinoma and squamous cell carcinoma of the lung are also positive in 90%, 60% and 20% of cases respectively. In hCG producing tumors, including also certain testicular and embryonic carcinomas, the beta chain is produced in higher quantities than the alpha or dimeric chains. hCG expression by non-trophoblastic tumors may indicate aggressive behavior. Positive control: JAR or TT Cells. Placenta.