Focal nodular hyperplasia (FNH) is a benign liver condition characterized by the presence of a well-defined mass in the liver. It is often discovered incidentally during imaging studies, such as ultrasound or CT scans, performed for other reasons. FNH is not cancerous and typically does not cause symptoms or require treatment. The exact cause of FNH is not fully understood, but it is believed to be related to abnormal blood flow in the liver. This condition is more common in women and usually occurs in individuals between the ages of 20 and 50. Regular monitoring is often sufficient, as FNH rarely leads to complications.