Histological features of intracranial germinomas not disappearing immediately after radiotherapy

The histological features of germinomas were investigated to differentiate tumors which completely disappear immediately after irradiation and those that persist. Eighteen previously untreated patients underwent germinoma biopsy and irradiation or combined irradiation and chemotherapy. Four tumors were located only in the pineal gland, eight in the suprasellar region, two in multiple locations, one in the basal ganglia, and three in other regions. Histologically, the germinomas could be divided into type A found in 13 cases which consisted mainly of large neoplastic cells and small lymphocytes, the so-called two-cell pattern, and type B found in five cases which consisted predominantly of fibrous tissue and granulomatous reaction containing occasional neoplastic cells. Follow-up computed tomography or magnetic resonance imaging showed the enhanced mass lesion disappeared in all cases of type A germinomas within 1 month after treatment, but persisted in all cases of type B germinomas for at least 1 month. Type B tumors required up to 12 months to show complete radiographic resolution. Persistent germinomas consisted predominantly of fibrous tissue and granulomatous reaction containing occasional neoplastic cells.