Netsiri Dumrongpisutikul
Pineal region tumors constitute 1% of all intracranial tumors.1 Among the various histologic types of pineal tumors, the germ cell tumors are more frequent than the pineal cell origin tumors.2 Our research aimed to differentiate between germinomas and pineal cell tumors based on ADC values and MR imaging characteristics. The previous literature suggests that the common pineal region tumors have no pathognomonic imaging features.3 DWI is an imaging technique based on molecular motion of water, which has been routinely integrated for tumor evaluation. The availability of the postprocessing software made quantitative measurement of ADC value feasible. However, information regarding diffusitivity of the pineal tumors has yet to be established.
Besides the younger age in germinomas, male preponderance in germinoma and pineal parenchymal tumor of intermediate differentiation (PPTID), and female preponderance in pineocytoma, the results of our study emphasize that quantitative signal value and degree of heterogeneity on conventional imaging (T1WI and T2WI) cannot differentiate germinomas from those pineal cell tumors. The most experienced neuroradiologist can predict the correct diagnosis based on conventional imaging characteristics alone in only 55% of cases. Integration of quantitative ADC measurement into imaging analysis helps differentiate these two disease entities. Germinomas have statistically significant higher mean ADC values than pineal cell tumors (1590.69 ± 532.96×10 -6 mm2/s vs 883.58 ± 317.48×10-6 mm2/s; P=.02). The ADC threshold was set to facilitate clinical application. The ADC threshold of 1250.00×10-6 mm2/s yielded high accuracy (89.5%), sensitivity (83.3%), specificity (92.3%), positive predictive value (83.3%), and negative predictive value (92.3%).4