Exophytic benign tumors of the liver: appearance on MRI

The purpose of our study was to determine the MR imaging appearance of exophytic benign liver tumors on precontrast and postgadolinium images. We reviewed our 9.5 year experience with MRI of the liver with dynamic gadolinium enhanced imaging to identify four patients with five histologically proven exophytic benign liver tumors. The histological diagnoses were cavernous hemangioma (2), focal nodular hyperplasia (FNH) (1), and hepatocellular adenoma (HCA) (2 exophytic adenomas in a patient with adenomatosis of the liver). All MRI studies were performed at 1.5 T and included: in-phase and out-of-phase T1-weighted spoiled gradient echo (SGE), T2-weighted fat-suppressed echo train spin echo, single shot T2-weighted sequences, and serial postgadolinium T1-weighted SGE sequences without and with fat-suppression. Prospective interpretations were reviewed and retrospective consensus readings of all MR images were performed assessing location, size, origin, morphology, visibility of the connection to the liver, signal characteristics on precontrast T1-weighted and T2-weighted images, and enhancement patterns on serial postgadolinium images. Three of the five tumors were pedunculated and connected to the liver by a thin stalk, which was prospectively identified in one patient. On precontrast and serial postgadolinium images, all exophytic tumors showed signal characteristics comparable to imaging features of standard intraparenchymal benign liver tumors. Our findings illustrate that the characteristic T1, T2, and postgadolinium imaging findings of these tumors permit correct identification of their liver origin despite their exophytic location, even if their connection with liver is not visualized.