Case Report: Focal nodular hyperplasia of the liver in an adolescent-a case report and literature review.

Focal nodular hyperplasia (FNH) of the liver is not a true neoplasm but rather a hyperplastic response to localized vascular malformations. In women of reproductive age, it is typically discovered incidentally and managed conservatively due to its benign nature. However, in adolescents, FNH demonstrates marked clinical heterogeneity. We present the case of a 17-year-old female patient with a hepatic lesion that increased in size to 6.0 cm within four months, exhibiting ambiguous imaging features. The central diagnostic dilemma lies in the need to differentiate FNH from hepatocellular adenoma (HCA), particularly high-risk subtypes, which may mimic classic imaging features of FNH while carrying significant risks of hemorrhage and malignant transformation. In this case, due to the inability to definitively exclude HCA through non-invasive modalities, laparoscopic partial hepatectomy was performed, and postoperative pathology confirmed FNH. A comprehensive literature review underscores that FNH exhibits substantial heterogeneity across the human lifespan, challenging the applicability of adult-centric management paradigms. Therefore, for adolescents with atypical hepatic lesions exceeding 5 cm and indeterminate imaging findings, proactive surgical intervention may offer definitive diagnosis and curative treatment, safeguarding long-term patient outcomes.