Atypical focal non-neoplastic brain changes in neurofibromatosis type 1: mass effect and contrast enhancement

Children and young adults with neurofibromatosis type I often have small hi gh-signal foci on T2-weighted images of the brain. We describe follow-up of two patients in whom one of the foci had atypical features, commonly regar ded as signs of a neoplasm. In the first, one lesion showed temporary contr ast enhancement and decreasing mass effect. The second developed an expandi ng lesion that increased minimally in size over 4.5 year's follow-up. The b orderline between neoplastic and non-neoplastic lesions seems to be indisti nct.