Germinoma laboratory tests

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Simrat Sarai, M.D. [2]

An elevated concentration of AFP and beta-hCG in the serum and CSF, and CSF cytology to detect malignant cells is diagnostic of intracranial germ cell tumors. In patients in whom endoscopic biopsy is not considered possible, detection of elevated tumor markers may be sufficient for diagnosis.

The following tests are done for intracranial germ cell tumors:

• CSF cytology to detect malignant cells
• Measurement of AFP and beta-hCG in the CSF and serum
  • Tumor marker levels are usually higher in CSF than in serum. In patients in whom endoscopic biopsy is not considered possible, detection of elevated tumor markers may be sufficient for diagnosis.
  • Measurement of beta-hCG and AFP in the CSF is more sensitive than serum levels in detecting abnormalities. However, due to discordant serum and CSF tumor marker results that were observed, both serum and CSF tumor markers should be obtained in the absence of clinical contraindications. Lumbar CSF is considered more accurate for tumor markers and cytology than ventricular CSF.
  • Tumor markers from ventricular CSF can be used, if a lumbar puncture is contraindicated.^[1][2]

• Laboratory studies to detect the hormonal dysfunction that may occur in patients with central nervous system (CNS) germinomas are as follows:
  • Diabetes insipidus
    • Serum sodium, serum osmolality, and urine osmolality
  • Hypopituitarism
    • Thyroid function tests, growth hormone levels, cortisol levels
  • Gonadal dysfunction
    • Testosterone level in males; prolactin level in females

Although elevated alpha-fetoprotein levels may be seen in the germ cell tumors; however, AFP levels may be normally elevated both in serum and CSF of neonates and infants. Alpha-fetoprotein (AFP) levels may be elevated in the following tumors:

• Pure endodermal sinus tumor (yolk sac)
• Embryonal carcinoma
• Malignant teratoma.

Interpretation of the AFP level must take into account the normal variation seen in this age group. The median AFP levels in CSF, in normal infants, are as follows:

Usually, pure germinomas and mature teratomas present with normal levels of AFP and beta-hCG in both serum and CSF. However, some histologically confirmed germinomas have elevated beta-hCG levels that are presumed to be due to beta-hCG secreting syncytiotrophoblasts. In beta-hCG secreting syncytiotrophoblasts, elevations of serum beta-hCG are generally limited (<50 IU/L), although some tumors have levels >100 IU/L.^{[3][4][5][6][7]} The relevant tumor marker findings is shown below in a tabular form:

Template:WikiDoc Sources