Abnormal diffusion-weighted MRI in medulloblastoma: does it reflect small cell histology? (original) (raw)

Medulloblastomas are malignant neoplasms composed of undifferentiated, small, round cells with high nuclear-to-cytoplasmic ratio. These tumors account for 30±40 % of posterior fossa tumors in children. We present a case of medulloblastoma with increased signal intensity on diffusion-weighted echoplanar MRI. We theorize that the densely cellular nature of medulloblastoma and the high nuclear-to-cytoplasmic ratio of this tumor restrict diffusion of water, causing increased signal on diffusion-weighted MRI.