What Causes Brain Shadow While Suffering From Breast Cancer?

Friend has Breast Cancer, had bad headaches, seeing "christmas" lights, got new glasses, had MRI and was told had a shadow on left behind ear area? Spinal fluid clear done twice. What is it? age 67 5feet tall, 220 lbs and just told "sugar'high at 375 and in Jan it was 140 taking Arimidex for breast cancer to shrink tumor now on it 3 mos. will have complete removal of left beast in early June MAYBE!
due to brain shadow....