Coronal view of MRI scan (with contrast) of brain from an 18 y/o female with history of neurofibromatosis 1. There is an irregularly shaped cystic mass in the left cerebellar hemisphere measuring approximately 4.0 cm. The image shows sharply delimited rim enhancement with an enhancing superior nodule. This appearance (large cystic mass with a brightly enhancing mural nodule), location (cerebellum) and association with neurofibromatosis 1 are all diagnostic of pilocytic astrocytoma. The diagnosis was confirmed on histology. Case produced with permission, courtesy of Dr. Frank Gaillard. Radiopaedia. Complete case is here.