 Each participant will undergo 8 visits of the course of the study. Each participant will have a baseline visit where a medical history will be taken, a physical, visual field test, electrocardiogram ECG, echocardiogram ECHO, and blood draw will be performed. At this point lapatinib therapy will begin and the patients will be asked to take the drug daily for the next six months. Patients will take Lapatinib 1250 mg daily orally, which is the standardized dose used to treat breast cancer patients. Visit 2 will be 1 month after the participant has started lapatinib. At visit 2 all participants will receive a physical exam, a history will be taken, an ECG will be performed, and a blood draw will occur. Visit 3 will be 2 months after starting lapatinib. A physical exam and history will be performed along with an ECG and echocardiogram and blood draw. Visit 4 will be 3 months after starting lapatinib. A physical, history, blood draw, ECG, visual field test, and a magnetic resonance imaging MRI of the pituitary will be performed. Visit 5 will occur 4 months after starting lapatinib. A physical exam and history along with a blood draw and ECG and echocardiogram will occur. Visit 6 will be 5 months after starting lapatinib. A physical exam, history, ECG, and a blood draw will occur. Visit 7 will occur 6 months after the start of lapatinib. A physical exam, history, blood draw, visual field test, ECG, echocardiogram and MRI of the pituitary will occur. At this point lapatinib will be discontinued. Visit 8 will occur 1 month after visit 7 and a physical exam, history, blood draw, and ECG and and echocardiogram will occur. 