Case History: Case M

A 53-year-old woman presented with headache, lethargy and numbness of the right upper extremity. She first noted a new type of headache about 6 months ago. Examination showed right homonymous hemianopia. A few days ago she had a focal motor seizure involving the right upper extremity. She had a previous history of breast cancer, diagnosed 2 years ago. Based on the history and the image shown, what is the most likely diagnosis?