MR imaging of pineal tumors.

MR images of pineal region tumors were analyzed in 26 patients with histologically proved tumors: seven germ-cell tumors, six astrocytomas, five teratomas, three pineoblastomas, two meningiomas, one dermoid, one epidermoid, and one metastasis. In an attempt to identify specific MR characteristics of these lesions, Gd-DTPA was administered to six patients. CSF and blood serum were assayed for alpha-fetoprotein (AFP) and human chorionic gonadotropin-beta subunit (HCG-beta) in 18 patients. MR findings were correlated with age, sex, the presence of biochemical tumor markers, and surgical outcome. We found that the most important factors in the determination of tumor type were the patient's age and the tumor markers. Increased levels of both HCG-beta and AFP were specific for patients with malignant teratomas and undifferentiated germ-cell tumors. HCG-beta alone was elevated in the patient with choriocarcinoma; only AFP was elevated in the patient with an endodermal sinus tumor. Tumor markers were not present in other patients in this series. The tumor size and the presence of fat were also helpful in determining tumor type. Hemorrhage was rare, seen only in the patient with a choriocarcinoma. Gd-DTPA did not enhance diagnostic specificity but aided in the detection of tumor seeding through CSF. We conclude that, although MR is sensitive in the detection of pineal region tumors and provides superb anatomic detail, MR signal characteristics are usually nonspecific. Correlation with the patient's age and the tumor markers significantly improves diagnostic accuracy.