Liver tumors are not a rare occurrence and a new Canadian study says their incidence may be increasing. Although some of these tumors are malignant, most are only benign tumors. Benign liver tumors are often only found incidentally when a patient undergoes ultrasound or similar analysis. Below is information on the different types of tumors that affect the liver, both benign and malignant.HemangiomasThese are by far the most common type of benign tumor that affects the liver. Between one and five percent of adults have these tumors, which are usually small and asymptomatic. Hemangiomas usually do not need to be removed unless they begin to bleed, which is rare even when they are large.Hepatocellular AdenomasThis type of benign tumor is known to occur often in adult women, especially those who are taking Birth Control, likely due to the overload of estrogen the liver is forced to process. It is not dangerous and usually only has to be removed when it grows so large that it causes pain and discomfort. This type of tumor rarely turns malignant.Focal Nodular HyperplasiaThis is a growth composed of multiple types of cells that is often diagnosed with the use of CT or MRI. Doctors sometimes order a biopsy to determine whether a case is malignant, which necessitates surgery to remove it. Surgery is also used when a case of FNH is causing pain for the patient.Other Benign Liver TumorsFibromas, or fibrous tumors, occur rarely, as do lipomas, which are usually asymptomatic. Another tumor that is not very rare is the benign bile duct adenoma.Malignant Liver TumorsMalignant tumors are spread by metastasis, the process of cancerous cells breaking away from a tumor and traveling through the bloodstream to invade new sites such as the liver. This is the dangerous type, as opposed to benign tumors, which do not metastasize and are often not harmful except by putting pressure on organs. Malignant tumors in the liver are treated with the standard therapies of radiation and chemotherapy as well as with surgery.