Pathological features of intracranial germinomas with reference to fibrous tissue and granulomatous change.

Intracranial germinomas are accompanied occasionally by a significant granulomatous change and abundant fibrous tissue, and this has made their pathological diagnosis difficult. However, the incidence of the granulomatous reaction and the presence of fibrous tissue together with their clinical characteristics in intracranial germinomas have not been fully investigated. Twenty-four germinomas, none of which had received preoperative treatment, were clinicopathologically examined. The location of the tumor was the pineal region (5 cases), the suprasellar region (13 cases), multiple lesions (2 cases), the basal ganglia region (1 case), and other regions (3 cases). Histologically, the germinomas could be divided into two types: (1) type A (18 cases) consisted mainly of large neoplastic cells and small lymphocytes, showing a two-cell pattern; (2) type B (6 cases) consisted predominantly of fibroinflammatory tissues containing occasional neoplastic cells (5/6 cases) and, rarely, neoplastic cells (1/6 cases). Perioperatively, two-cell-pattern germinomas (type A) were characterized as soft tumors and fibroinflammatory germinomas (type B) as hard tumors. Thus, the fibroinflammatory type B accounted for 25% of the intracranial germinomas. Although there were no topographical and clinical differences between the two types, we conclude that immunohistological studies to detect neoplastic germ cells are warranted in cases of small stereotactic biopsies of hard type B tumors.