Focal nodular hyperplasia is a type of benign tumor that appears in the liver. Most people with the condition do not experience any adverse symptoms, and the tumors are usually only discovered when patients receive diagnostic imaging tests for other health problems. The tumor does not turn malignant and rarely grows large enough to create any lasting problems. When it is detected, however, healthcare providers usually conduct careful screenings to ensure that it is not a similarly shaped cancerous mass called hepatocellular carcinoma.
Medical researchers have determined that focal nodular hyperplasia results from abnormal proliferation of a specialized type of liver cell called a hepatocyte. Irregular hepatocyte production is caused by a congenital defect in the blood vessels that feed the liver. Upon careful inspection, a medical examiner can identify a central scar in the tumor where a malformed vessel distributes blood to the hyperplasia. Medical professionals can further distinguish abnormal hepatocytes from surrounding healthy tissue because they generally appear lighter in color.
Focal nodular hyperplasia tends to affect women much more frequently than men, though experts are unsure why that is the case. Most patients diagnosed with the condition are over the age of 30. Tumors do not affect liver functioning or cause physical symptoms in the vast majority of cases. Rarely, a tumor can grow large enough to put pressure on the liver and surrounding organs, leading to abdominal pain. A chemical that is found in oral contraceptives can trigger a hemorrhage in the tumor, though excessive bleeding is very rare.
It is common for this type of tumor to go unnoticed until the growth is seen in diagnostic imaging tests for other conditions. A medical professional who is screening for cancer, internal injuries, or other disorders near the abdomen may notice the abnormal mass of hepatocytes. Once it is discovered, healthcare providers commonly perform additional screening tests and take a biopsy of tissue to make sure that the tumor is not malignant.
After screening for cancer, most instances of focal nodular hyperplasia are left alone. Tumors usually stay about the same size and may not result in symptoms. If a patient experiences significant abdominal pain, however, surgery may be necessary to provide relief. In some cases, healthcare professionals are unable to determine whether a tumor is benign or malignant, and if there is any question that a tumor may be cancerous, surgery or radiation therapy is highly recommended.