Focal nodular hyperplasia: Natural course observed with CT and MRI

Purpose: The purpose of this work was to assess the natural course of biops y-proven focal nodular hyperplasia (FNH). Method: Eighteen biopsy-proven FNHs in 14 patients (12 women and 2 men) who were followed for at least 6 months with CT and/or MRI were included in th e study. The volume of the lesions was calculated twice by two observers us ing the summation of areas method. Intra- and interobserver variability was assessed by intraclass correlation coefficients. Longitudinal data analysi s was performed with generalized estimating equations. Results: The volume of FNH was stable in 6 cases, decreased in 10 cases, an d increased in 2 cases. Intra- and interobserver variability in size measur ements was 5-10%. Intraclass correlation coefficients were >0.992. Longitud inal data analysis showed that there was a general trend of lesion regressi on. Conclusion: Long-term follow-up and objective measurements performed in pat ients with biopsy-proven lesions show that the natural course of FNH is var iable. In particular, lesion regression is not rare.