Teaching NeuroImages: brain mass with hilar adenopathy: the importance of histologic diagnosis.

A 30-year-old man presented with weeks of progressive headaches, imbalance, and aphasia. Brain MRI revealed an enhancing left frontal mass (figure 1, A and B). Chest imaging revealed mediastinal and hilar adenopathy (figure 1, C and D). Metastatic cancer was initially suspected, but pulmonary lymph node aspiration revealed sarcoidosis (figure 2A). Subsequent brain biopsy revealed glioblastoma (figure 2B).