Large heterogenous cystic mass left posterior parieto-occipital lobe, involving left splenium of corpus callosum. Adjacent moderate peritumoral edema and mass effect, partially compressing occipital horn of left lateral ventricle.  Mass shows peripheral ring enhancement with central fluid component and necrotic component posteriorly.   No ventricular compression or midline shift. 
Rest of brain parenchyma appear normal with no other enhancing lesion.   
Findings consistent with large cystic Astrocytoma / Glioblastoma Multiforme or cystic metastasis.  
 