B-hCG (Human Chorionic Gonadotropin)

Accurate (1039), American Research Products (1C5), Biodesign ([427,681], [812,813], [827,829,830], [827,31], 2B1-3, ME.1, ME.106, ME.108, polyclonal), Biogenesis (2F4/3, BIO-BCG-001, BIO-BCG-005, BHCG-010, polyclonal), Biogenex (D7), Caltag Laboratories (2092), Dako, Fitzgerald (M15292, M15294, M94138, M94139, M94140, M94141, polyclonal), Immunotech (2B1.3), Sanbio/Monosan (2092) and Zymed (ZMCG13, ZSH17).

These antibodies are applicable to both formalin-fixed, paraffin-embedded sections and to frozen sections. Neither enzyme digestion nor HIER appears to enhance immunoreactivity.

Human chorionic gonadotropin (hCG) is a glycoprotein (40 kD) comprising a protein core and a carbohydrate side chain (Bellisario et al, 1973). The molecule is composed of two dissimilar subunits -a and b. The a subunit is indistinguishable immunologically from thea subunit of pituitary glycoprotein hormones: luteinizing hormone (LH), follicle-stimulating hormone (FSH) and thyroid-stimulating hormone (TSH). The b subunits are different from each other and confer specificity. hCG, secreted in large quantities by the placenta, normally circulates at readily detectable levels only during gestation (Braunstein et al, 1976).
The monoclonal antibody (IgG1) to b-hCG was produced by immunization with pure chorionic gonadotropin b subunit. b-hCG is demonstrable in syncytiotrophoblasts of normal human placenta.

hCG is the most important marker of gestational trophoblastic cells, being present in syncytiotrophoblastic cells and cells of the intermediate trophoblast but absent in cytotrophoblast (Appendices 1.29, 1.30). In syncytiotrophoblast cells, hCG is demonstrable from the 12th day of gestation, reaches a peak at 6 weeks and decreases thereafter; at term hCG is present only focally in these cells. In choriocarcinoma strong diffuse immunostaining for hCG occurs in syncytiotrophoblastic cells (and focal immunostaining for human placental lactogen). In contrast, placental site trophoblastic tumor shows focal hCG immunopositivity (and diffuse human placental lactogen immunoreaction) (Appendix 1.29).
b-hCG expression in non-trophoblastic tumors may indicate aggressive behavior of the tumor. It is worth noting that hCG may be demonstrated in 14% of patients with hepatocellular carcinoma (Braunstein et al, 1973). hCG may be demonstrated in the trophoblast-like cells which develop in undifferentiated carcinoma of the endometrium (Pesce et al, 1991); however, the presence of recognizable glandular structures and the lack of the biphasic pattern of alternating rows of syncytial and cytotrophoblasts rule out the possibility of choriocarcinoma. hCG has also been demonstrated in poorly differentiated areas with cells resembling syncytiotrophoblasts in three women with serous papillary or mucinous adenocarcinomas of the ovary (Civantos & Rywlin, 1972). In 6-8% of dysgerminomas, there are individual or collections of syncytiotrophoblastic giant cells that contain/produce hCG.

•Bellisario R, Carlsen RB, Bahl-Om P 1973. Human chorionic gonadotropin. Linear amino acid sequence of the a subunit. Journal of Biology and Chemistry 248: 6796-6809.

•Braunstein GD, Vogel CL, Vaitukaitis JL, Ross G 1973. Ectopic production of hCG in Ugandan patients with hepatocellular carcinoma. Cancer 32: 223-226.

•Braunstein GD, Rasor J, Danzer H et al 1976. Serum human chorionic gonadotropin levels throughout normal pregnancy. American Journal of Obstetrics and Gynecology 126: 678-681.

•Civantos F, R wylin AM 1972. Carcinomas with trophoblastic differentiation and secretion of chorionic gonadotrophins. Cancer 29: 789-798.

•Pesce C, Merino MJ, Chambers JT, Nogales F 1991. Endometrial carcinoma with trophoblastic differentiation: an aggressive form of uterine cancer. Cancer 68: 1799-1802.

Manual of diagnostic antibodies for immunohistology / Anthony S.-Y. Leong, Kumarasen Cooper, F. Joel W.-M. Leong.