Abstract
Computerized tomography (CT) of 16 pineal region tumors including germ cell tumors arising in sites other than the pineal region was studied from the point of view of differential diagnosis and management of these tumors. They included 10 germinomas, three teratoid tumors (malignant teratoma), one teratoma, one ependymoma and one meningioma.
Germinomas showed characteristic CT findings: they were noted as heterogenous and irregularly-defined masses with slightly or moderately high absorption from 20 to 30 EMI numbers (old EMI numbers) in plain scans, which were moderately enhanced in contrast scans, presenting rather well-defined masses. This CT finding was commonly noted in germinomas of the pineal and suprasellar regions as well as in germinomas invading the periventricular region or subarachnoid space. Another outstanding value offered by CT in the diagnosis of germinoma was recognition of the extremely high radiosensitivity of this tumor. Areas of high absorption except calcification in germinomas completely disappeared after chemoradiotherapy using Bleomycin, ACNU and Vincristine. Minimal radiation doses until complete disappearance of the high density lesion were mostly less than 1, 000 to 2, 000 rads.
One teratoma also showed a very characteristic CT finding: a well-defined mass contained multiple, irregular calcified lesions surrounded by areas of low absorption with a wide variety of EMI numbers from minus 9 to plus 10, suggesting the presence of cysts and fatty tissue. No area of this tumor was enhanced by contrast medium except for small areas of soft tissue which showed a very slight enhancement.
In three teratoid tumors, two embryonal carcinomas and one teratoblastoma, plain scans revealed isodense masses which were markedly enhanced by contrast medium. This enhancement was well-correlated with angiographical demonstration of a dense tumor stain. However, similar CT findings were noted in one ependymoma and one meningioma of the pineal region. The teratoid tumors and ependymoma were radioresistant.
These observations show that germ cell tumors in the pineal region such as germinoma, teratoma, or teratoid tumors which frequently occur specifically in the Japanese population could be differentiated from each other by CT before treatment, and that a small dose irradiation could confirm the diagnosis of germinoma.
