Focal nodular hyperplasia of the liver--an imaging conundrum.

Focal nodular hyperplasia is a common benign tumour of the liver that usually does not require treatment. This tumour can be difficult to distinguish noninvasively from other lesions in young patients that may require intervention, such as hepatic adenoma and fibrolamellar carcinoma. The authors report three cases of histologically proven focal nodular hyperplasia and one case in which the imaging features strongly suggested this tumour. These cases illustrate many of the variable imaging features of focal nodular hyperplasia. The authors review the typical imaging findings for focal nodular hyperplasia, hepatic adenoma and fibrolamellar carcinoma, indicate the areas of overlap that make noninvasive diagnosis impossible and discuss the role of percutaneous biopsy in establishing the definitive diagnosis.