Neuroimaging diagnosis of pineal region tumors-quest for pathognomonic finding of germinoma.

INTRODUCTION: Our study aimed to elucidate the imaging features for the differentiation of pineal germinoma and other pineal region tumors.

METHODS: Image data sets of computed tomographic (CT) scan and magnetic resonance imaging (MRI) data of 93 pineal region tumors including 33 germinomas, 30 nongerminomatous germ cell tumors (NGGCTs), 20 pineal parenchymal tumors (PPTs), and 10 miscellaneous tumors of pineal region were reviewed. Imaging features on CT and MRI were qualitatively assessed by three readers. To know the reasons for morphological differences between germinomas and NGGCTs, histological investigation was done.

RESULTS: Localized calcification was seen in more than 70 % of germ cells tumors (GCTs: germinomas and NGGCTs) while it was scattered in more than half of PPTs. Cystic components in tumors were most frequent in NGGCTs (62 %). Multiplicity of lesion was restricted to GCTs: 39.4 % in germinoma and 10.0 % in NGGCTs. Thick peritumoral edema was more frequent in germinoma than in NGGCT: 40.6 vs. 14.8 % (p=0.0433, Fisher's test). Bithalamic extension of tumor was seen in 78.8 % of germinomas. It was significantly rare in other groups of tumors (p<0.0001, Fisher's test). The relative collagen amount per unit area was significantly lower in germinoma than in NGGCTs.

CONCLUSION: By paying attention to characteristic features as bithalamic extension, thick peritumoral edema, calcification pattern, multiplicity, and their combination, the preoperative differential diagnosis of pineal germinoma will become more accurate.