Differentiation of Germinomas from Other Tumors in the Pineal Region with CT and MR Imaging, with Special Reference to Extension Patterns to the Thalami

To determine the computed tomography (CT) and magnetic resonance (MR) characteristics of pineal region germinomas, the author reviewed images from 40 patients with pineal region tumors. These tumors were divided into two groups: those with germinomas (n =17), and those with other tumors in the pineal region (5 with a germ cell tumor other than germinoma; 8, mixed germ cell tumor; 8, pineal parenchymal tumor; and 2, miscellaneous tumors; n = 23). All cases were investigated with CT; 31 of the cases were also investigated with MR imaging. The following parameters comprised statistically significant differences between the two groups: maximum size of the tumor, tumor density of the precontrast CT, signal intensity of precontrast T1-weighted spin-echo images, and homogeneity of the tumor on both precontrast and postcontrast studies. This study found that extension patterns of pineal region tumors into the thalamus have significant implications in differentiating germinomas from other tumors of this region. Germinomas are characterized by thalamic extension without lateral displacement of the third ventricle walls due to direct compression by tumors (P =.0034). The analysis of tumor extension patterns, combined with the parameters mentioned above, may provide a more accurate differential diagnosis in pineal region tumors, leading to prompt and appropriate treatment