MR imaging of focal nodular hyperplasia of the liver.

The magnetic resonance appearance of three lesions of focal nodular hyperplasia observed in two patients is reviewed. All three lesions demonstrated isointensity with the liver on the short repetition time (TR) and echo time (TE) spin echo images. One lesion also showed a central area of low signal intensity that pathologically corresponded to a scar. The long TR and TE images had a varied appearance, from mixed high signal intensity to predominantly isointense with the liver. The histopathology for each lesion was carefully reviewed. The primary microscopic difference between the lesion that was predominantly isointense with liver on the long time TR and TE images and the other two, which were of mixed high signal intensity on the long time TR and TE images, was the former's relative lack of fibromuscular obliteration of septal blood vessels in the scar. Focal nodular hyperplasia can have at least two possible appearances at 1.5 T; in these three lesions there was consistent isointensity with the liver on the short TR and TE images.