 Craneoferringiomas are rare brain tumors that affect about 400 people in the United States each year. These tumors usually grow very slowly and don't look very aggressive under a microscope. They are considered benign. However, having a mass inside of the brain can be dangerous. Craneoferringiomas start growing next to the optic nerves and the hypothalamus which controls eating. When these tumors develop, patients can experience life-long, devastating symptoms such as widespread hormone imbalances, blindness, and uncontrollable eating and obesity. Surgery and radiation therapy have been the only treatments, but they also have serious side effects because the tumors are located so close to critical areas of the brain which get damaged with these interventions. Unfortunately, there are no effective targeted therapies for these types of tumors. Let's take a step back and understand what Craneoferringiomas really are. There are two types of these brain tumors. The adamantinomatis, which occurs in children and adults, and the papillary type, which occurs almost entirely in adults. Last year, a team of scientists in Boston, along with collaborators in Baltimore, Philadelphia, and Cairo, Egypt showed that each type of tumor has its own set of distinct genetic mutations. The adamantinomatis tumors are driven by mutations in beta-catenin, and the papillary tumors are driven by mutations in BRAF. These mutations turn on their respective genetic programs, which causes the cells to divide uncontrollably and form tumors. No therapies have been approved to block beta-catenin. However, BRAF is also involved in many common cancers such as melanomas, so a lot of progress has been made to try to turn off BRAF, and a number of powerful drugs now exist that do just that. Based on these findings, clinicians and scientists can look at the DNA in a patient's tumor and determine what type of tumor it is, and perhaps what type of treatment should be used, like a BRAF inhibitor in the case of a papillary tumor. This is the idea behind precision medicine, and that's exactly what a team at Massachusetts General Hospital and Brigham & Women's Hospital in Boston did. Their work was published in the Journal of the National Cancer Institute in 2015. Using precision medicine, doctors treated a man who had uncontrollable papillary craniopharyngeoma. Before starting treatment, the tumor was growing rapidly and damaging critical areas of the brain. The brain surgeons removed it several times, but it kept growing back. The patient was nearly blind and very sick. After a close look at the tumor's DNA, the team of doctors found a BRAF mutation, which gave them an idea to start a new therapy that had worked for melanoma, targeting BRAF and another partner protein that helps BRAF function. Remarkably, in one month, the drug treatment not only stopped the tumor from growing, but it shrunk the tumor by 90%. The patient then received radiation therapy and months later is still doing well. With this experience, the team of doctors is now planning a clinical trial to test this drug combination in a larger set of craniopharyngeoma patients based on the mutations in the tumor DNA, the precise drug for the precise tumor. If successful, this therapy regimen could revolutionize the treatment of some craniopharyngeoma patients, but many questions still remain. Will all papillary tumors respond this well? Will tumor cells figure out a way to grow despite this treatment? And can we figure out clever ways to entirely change the way that these patients are treated? For example, when a patient has a brain mass that is suspected to be a craniopharyngeoma, can doctors draw blood to detect tumor DNA and look for BRAF mutations to confirm the diagnosis without surgery? In other words, can they do a liquid biopsy of the tumor? And after diagnosis, will treating these patients with precision medicines result in fewer lifelong complications and disabilities? This is one promise behind the precision medicine approach. And in this patient, precision medicine was the answer. Only time will tell if this exciting idea will become a reality for other cancer patients of all shapes and sizes.