Human chorionic gonadotrophin immunoactivity in cystic intracranial tumours.

BACKGROUND AND OBJECTIVE

With regard to intracranial tumours, elevated hCG in CSF or serum has been considered to be specific for germ-cell tumours. Recently however, elevated hCG has also been shown to be present in cyst fluid and CSF of patients with craniopharyngiomas. While germ-cell tumours are generally non-cystic, the aim of our study was to determine the significance of hCG in cystic intracranial lesions.

DESIGN

In a prospective study, hCG immunoactivity and subunits of hCG were measured in cyst fluid, CSF, and serum of patients harbouring intracranial cyst lesions.

PATIENTS AND MEASUREMENTS

hCG immunoactivity was measured in cyst fluid and serum samples of 42 patients. CSF samples were available from 12 patients with craniopharyngiomas. In order to fully characterize the hCG immunoactivity, we used immunoradiometric assays for total hCG activity (measuring both intact hCG and the free beta-subunit of hCG), and those specific for intact, dimeric hCG (hCG), free beta-subunit of hCG (hCG beta) and free alpha-subunit. Furthermore, immunostaining of tumour tissue was performed using monoclonal antibodies directed against the free beta-subunit of hCG.

RESULTS

Total hCG immunoactivity was markedly elevated in cyst fluid of all 17 craniopharyngiomas (range 36.7-4558 IU/I; normal < 5 IU/I). Moderately elevated levels of hCG in cyst fluid were detected in three of four pituitary adenomas, in two metastases from lung cancer and in two arachnoid cysts. hCG beta was detected in cyst fluid from all hCG positive cysts, while specific determination of intact (dimer) hCG and alpha-subunit mostly yielded negative results. No hCG immunoactivity was found in cystic gliomas, meningiomas or haemangioblastomas. hCG was elevated in CSF of two patients with craniopharyngiomas, but no hCG immunoactivity was detected in any serum sample. Subtle immunostaining of epithelial cell groups was shown in five of ten craniopharyngiomas. Clear immunostaining for hCG beta was also found in scattered epithelial cells of one pituitary adenoma.

CONCLUSIONS

hCG immunoactivity in cystic intracranial lesions is due mainly to hCG beta. Measurement of hCG immunoactivity in cyst fluid can be helpful in the differential diagnosis of intracranial cystic lesions, if surgery is restricted to cyst decompression and no histology is available. High levels suggest a craniopharyngioma.