I had a liver biopsy performed last week because I have had a "knot" in that area that has been causing me some discomfort for the past 10 years. According to the biopsy, it is "nodular hyperplasia." The doctor compared it to a sort of birthmark, and said it probably has been there all of my life. Can you tell me more about this, and what can be done to treat it?

K.

It sounds like the diagnosis you were given is focal nodular hyperplasia (FNH). FNH is a condition in which a nodule, composed of a central scar tissue and clumps of surrounding liver cells, is found within an otherwise healthy liver. The size of the nodule in FNH can vary in size.

In most cases, FNH does not cause symptoms and is found only when the patient has an imaging study of the abdomen (ultrasound or CT scan) for another reason. Less frequently, FNH can cause pain, which is thought to be related to situations in which the lesion may bleed.

The cause of FNH is uncertain. Some speculate it is caused by abnormal development of small blood vessels in that segment of liver. This theory is supported by the finding of abnormal-appearing vessels in the nodule of FNH. However, others think that FNH is caused by, and perpetuated by, hormones. There is some evidence that FNH nodules can enlarge in women who are on contraceptive drugs that contain hormones. In very rare instances, the nodule has even ruptured in such women.

The diagnosis of FNH is usually made through a combination of imaging tests (including ultrasound, CT and/or MRI scans). In some cases, an arteriogram may be needed to fully characterize this lesion, and a biopsy may also be done. It is important to thoroughly evaluate any type of growth on the liver to rule out liver cancer, which may sometimes appear similar to a nodule. However, it is important to note that there is no evidence that FNH is associated with, or develops into, cancer.

The treatment of FNH is controversial. Most experts recommend surgery to remove large nodules or those that are causing pain. Smaller nodules are often left alone and followed with periodic imaging tests to monitor their size. If FNH is not removed in a female patient, she is advised not to take contraceptive hormones or to become pregnant because of the theoretical risk of rupture.