Pineal Region TumorsPatients with pineal region tumors usually present with the acute effects of these tumors compressing and obstructing the nearby ventricular system, causing hydrocephalus (excess fluid in the chambers of the brain), raised pressure within the entire brain and consequently headaches and vomiting. Characteristically, certain eye changes are also noted due to downward compression of the tumor on the midbrain (Parinaud’s Syndrome). A magnetic resonance imaging (MRI) scan will reveal a tumor in the pineal region – but that in itself does not confirm the diagnosis of a germ cell tumor. Other tumors can look virtually identical on MRI, such as pineoblastoma (pineal PNET), ependymoma Suprasellar/hypothalamic Region TumorsPatients with suprasellar/hypothalamic region tumors present usually with a much longer history, sometimes over many months or even years, of vague symptoms including increased thirst and urination, increased fatigue, poor growth and declining school performance. These signs are largely due to destruction of the hormone-producing cells located in the hypothalamus and its connection down to the pituitary gland (the pituitary stalk or infundibulum). Again, an MRI scan will demonstrate a tumor in this location, but this does not confirm the diagnosis of a germ cell tumor; gliomas of the optic pathway are not infrequently confused with germ cell tumors in this location, as can other types of tumors. Tumor MarkersOne of the unique characteristics of germ cell tumors arising in the brain is their production and release of chemicals into the blood and the cerebrospinal fluid (CSF) called tumor markers. The presence of these tumor markers in either location can often confirm that a tumor seen in the pineal or suprasellar regions on MRI is indeed a germ cell tumor. There are two germ cell tumors markers in common use today, but not all germ cell tumors produce them, and some do so only in small amounts. The presence of such markers and the levels at which they are present in the blood or CSF are not absolutely diagnostic of specific germ cell tumor types. These tumor markers can thus be misleading in identifying germ cell tumors and specific germ cell tumor types, so that the results of germ cell tumor marker tests must be interpreted with caution. The germ cell tumor markers and their associated tumor types are shown below:
A significant problem that now exists is that some children with pure germinomas are being over-treated as more malignant tumors. This is because an HCG-ß level in excess of 25mg/dl is currently, on North American and European (but not Japanese) trials, considered diagnostic of a more malignant choriocarcinoma tumor. There is no basis in fact for such an arbitrary cut off. On the contrary, it is clear that children with pure germinomas can have much higher levels of HCG-ß in their blood or CSF. At Children’s Hospital of Los Angeles, biopsy proven children with germinomas and with HCG-ß up to almost 200mg/dl have been successfully cured with the less intensive germinoma treatments. |