A central nervous system
germinoma is curable in most cases by
radiotherapy, and most of the
tumor mass disappears promptly after 20-30 doses. However, some
germinomas take a longer period to vanish completely from magnetic resonance imaging (MRI) or computed tomography (CT) scans. In such cases, the
tumor may contain components such as
teratoma. The aim of this study was to clarify the nature of the persistence of some
germinomas. Five cases of histologically verified
germinoma in which
radiotherapy was performed to treat
residual tumor were selected. The doses of focal
radiotherapy and whole brain
radiotherapy were 10-20 Gy and 20-34 Gy, respectively. In these cases, correlation was made between the degree of persistence of the
tumor when assessed by MRI and the amount of interstitial content, as determined by histology. The histological evaluation, using
hematoxylin-
eosin stain,
silver impregnation and Azan staining was carried out independently of clinical information. The
tumor vanished soon after
radiotherapy in three cases, but 3-15 months passed before the
tumor completely vanished from the MRI scans in the other two cases. The histology of the cases in which the
tumor disappeared rapidly was predominantly of large
tumor cells and only small amounts of
reticulin. However, in the persistent
tumors, large amounts of
reticulin and vascular components were present. Thus, it is proposed that
tumors with a large parenchymal component disappear soon after
radiotherapy, whereas
tumors composed mainly of interstitial component persist. Long-standing enhancement seen on MRI or CT scans of patients with an intracranial
germinoma is indicative of a large amount of interstitial component in the
tumor.