A 58-year-old man from Mumbai presents with a 3-month history of progressive cognitive decline, personality change, and recent-onset seizures. His wife reports he has become withdrawn and forgetful. MRI brain shows a large, heterogeneous mass centered in the left temporal lobe with significant perilesional edema. The lesion is predominantly hypointense on T1 and hyperintense on T2/FLAIR. Post-contrast imaging reveals irregular, patchy enhancement with areas of necrosis. There is mass effect with midline shift. What is the most likely diagnosis?