Focal Nodular Hyperplasia
Focal nodular hyperplasia (FNH) is a common, benign liver lesion made up of normal liver cells arranged around a central scar. It is not a cancer and does not become one. Most cases are found incidentally during imaging performed for unrelated reasons, and the majority of people with FNH have no symptoms. Because of its characteristic appearance, imaging—especially MRI—usually provides a confident diagnosis without the need for biopsy.
What is it?
Focal nodular hyperplasia is a benign growth made of normal liver tissue arranged in a slightly abnormal pattern. It typically features a central scar with radiating fibrous bands, which can be seen on imaging and helps distinguish FNH from other liver lesions. The exact cause is unclear, but it is believed to develop in response to altered blood flow within the liver.
FNH does not grow aggressively, spread, or transform into cancer. Many lesions remain stable for years, and even when growth occurs, the condition remains benign. MRI with contrast is especially helpful because it highlights the characteristic features of FNH, allowing radiologists to make a confident diagnosis.
Important to Know
Focal nodular hyperplasia almost never requires treatment. It is considered a “do-not-touch” lesion in most cases because intervention is unnecessary and carries more risk than benefit. Follow-up imaging is sometimes performed if the initial appearance is not classic or if symptoms develop, though symptoms from FNH are uncommon.
Red flags—such as severe abdominal pain, fever, jaundice, or unintended weight loss—are unlikely to be caused by FNH and should prompt evaluation for other conditions. When the imaging appearance is typical, patients can be reassured that the lesion is benign and does not increase the risk of liver cancer.