Focal Nodular Hyperplasia (FNH) is the second most common benign liver lesion after hemangiomas, affecting <5% of the general population, with a strong female predominance. Like hemangiomas, growth is not hormone dependent, and OCPs or pregnancy are not contraindicated.  - Definition = Benign hyperplastic proliferation of unencapsulated hepatocytes caused by a localized vascular malformation. Histology shows normal hepatocytes, bile ducts, and Kupffer cells, often with a central stellate scar. No malignant potential.  - Imaging characteristics = Demonstrates homogeneous arterial hyperenhancement with a characteristic central stellate scar that is hypoenhancing early and enhances on delayed phases. Lesion is iso- to mildly hyperintense on T2, with the scar classically T2 hyperintense. On hepatobiliary phase MRI, the lesion is iso- or hyperintense due to retained contrast from functioning hepatocytes, distinguishing it from adenoma.  - Subtypes - Classic FNH (with central scar, bile duct proliferation)  - Non-classic FNH (atypical histology, lacking some features)  - Special consideration = Fibrolamellar hepatocellular carcinoma (FLHCC) can have similar imaging and may be confused with FNH. FLHCC is usually a larger tumor with, often, nodal metastasis and hypointense central scar in T2-weighted images. Resection with negative margins is the treatment of choice in localized disease.  - Treatment & Surveillance - Typical FNH on imaging: no treatment or surveillance required.  - Indeterminate cases: biopsy or resection if diagnosis cannot be distinguished from adenoma or malignancy.  - Large, symptomatic lesions can be considered for surgical resection after thorough evaluation for other causes of symptoms.  - No surveillance role after complete resection unless pathology is indeterminate.