Evolution of focal nodular hyperplasia during long-term ultrasound follow-up: results from a single-center study

Purpose: To examine the natural history of focal nodular hyperplasia (FNH) lesions through long-term ultrasound (US) follow-up and assess the relationship between clinical characteristics and size changes. Methods: We retrospectively enrolled 55 patients diagnosed with FNH who were followed with ultrasound for at least 24 months. A total of 94 FNH nodules were included in the final analysis. A significant change in size was defined as an increase or decrease of 0.5 cm or more, and nodules were classified as increased, decreased or stable. Additionally, we analyzed the association between clinical data and changes in nodule size. Results: The mean follow-up duration between the initial US examination at diagnosis and the last available examination was 58.3 ± 33.5 months (range: 24.2–186.6). The majority of nodules remained stable (47.9%) or decreased in size (35.1%), while a small proportion of nodules disappeared (11.7%) and only 7.3% showed an increase in size. No significant association was found between size variation and factors such as oral contraceptive use, pregnancy, BMI or follow-up duration. Conclusion: Changes in the size of FNHs during follow-up are relatively common, with most lesions remaining stable or undergoing regression or disappearance over time. These size variations do not appear to be influenced by hormonal factors or other clinical characteristics.