germ cell tumors of the central nervous system
Friday 20 January 2012
germ cell tumor of the central nervous system
Primary CNS GCT consists of several subtypes with different degrees of histological differentiation and malignancy.
According to histological differentiation, related tumor markers, and secreted protein markers, these tumors can be classified into germinomas and nongerminomatous GCTs (NGGCTs), the latter including embryonal carcinoma (EC), yolk sac tumors (YST), choriocarcinoma (CC), teratoma (mature teratoma, immature teratoma, or immature teratoma with malignant differentiation) and mixed GCTs.
For NGGCTs, except for benign mature teratoma, all of the other tumors present with diverse malignancies and therapeutic sensitivities when compared to germinomas and are grouped together as nongerminomatous malignant GCTs (NGMGCTs).
NGMGCTs require more extensive drug and irradiation treatment regimens, have a higher recurrence rate and a lower survival rate [7,8]. Clinically, >50% of pediatric CNS GCTs are germinomas, while the majority of remaining tumors are NGMGCTs.
Histologically, germinoma is the most undifferentiated GCT and is composed of undifferentiated large cells that resemble primordial germinal elements.
Among the NGGCTs, the histological picture differs depending on the diagnosis.
EC contains undifferentiated stem cells resembling the embryonic inner cell mass (ICM).
YST and CC correspond to the extra-embryonic differentiation along mesoblast and trophoblast lines, respectively.
This contrasts with teratomas, which consist of differentiated derivatives that include all three germ layers with or without incompletely differentiated tissue elements, like neuroepithelium, which resembles fetal tissue.
CNS GCTs often present with more than one histological component and are then classified as mixed GCTs.
The comparative incidences are 15.3% in Japan, 14.0% in Taiwan, 11.2% in Korea, 2.3% in USA, and 2.5% in German in various reported series.