Spontaneous regression of focal nodular hyperplasia of the liver.

Focal nodular hyperplasia (FNH) of the liver is a rare benign lesion that probably reflects a local hyperplastic response of hepatocytes to a vascular abnormality. Currently, the natural history of the disease remains largely unknown. We present a patient with FNH of the liver who was followed up for 4 years. A 22-year-old woman with a 3-year history of oral contraceptive use was referred to our hospital in September 1996 for further examination of a liver tumor. A diagnosis of FNH was made using various imaging methods, such as ultrasonography, enhanced computed tomography (CT) scanning, MR imaging, and hepatic angiography, as well as fine-needle biopsy. A decrease in the size of the lesion was observed by enhanced CT scanning during the 4-year observation period. In this patient, oral contraceptive use and its discontinuation may have influenced the natural history of FNH. The present case suggests that an accurate diagnosis is of the utmost importance, and a patient with FNH should be managed conservatively rather than by resection, because FNH has the potential for spontaneous regression with the discontinuation of oral contraceptives.