a. Focal Nodular Hyperplasia (FNH): This is the most common benign solid liver nodule, accounting for up to 60% of cases. FNH is a non-cancerous lesion that develops due to an overgrowth of normal liver cells in response to a variety of stimuli, such as hormonal changes, inflammation, or vascular malformations. FNH is typically solitary, round, and well-defined, with a central scar.