Liver cell adenomaD13.4

Rare, monoclonal, 1-10cm large, mostly solitary, yellow-brown, benign node of the liver delimited by a pseudocapsule.

The adenoma cells carry specific somatic mutations that correlate with the histological characteristics (Thomeer MG et al. 2014):

• HNF1 mutations (hepatocyte nuclear factor 1α-mutated HCA); this type is associated with fatty hepatocytes
• Mutations in the gene for beta-catenin with dysplasia and malignant transformation
• The telangiectatic adenoma (inflammatory adenoma) with dilated sinus vessels and inflammatory infiltrates has been described as the 3rd type
• Non-classifiable hepatocellular adenomas

The annual incidence is estimated at 1:1,000,000.

Tumor growth probably hormone-induced. Adenomas not only occur more frequently in women taking estrogen-containing preparations, but they are also larger (up to >10cm) and have an increased risk of bleeding. After discontinuing the estrogen-containing preparations, adenomas often regress. Other predisposing factors are long-term use of anabolic steroids, the presence of glycogenosis (glycogen storage diseases) type III and IV, a congenital porto-caval shunt. HA rarely occurs in children (Dhingra S et al. 2014).

Mostly women of childbearing age. The mean age at diagnosis is 34 years (range 15-64 years).

Typically HA is solitary, but patients with multiple tumors have also been described as "Hepatocellular Adenomatosis". The size varies between about 1 cm (the detection limit for common imaging techniques) and > 10 cm. If the diameter of the HA is < 5 cm, there seems to be no risk of complications for the carriers. Rarely, and then more frequently in men, very large tumours may show signs of malignancy.

Most patients with HCA experience no symptoms. The diagnosis is usually made by chance during a laparatomy or a routine abdominal imaging examination for other reasons. Pain or discomfort in the right upper abdomen or epigastrium is common but not always related to the adenoma.

Liver value changes are rare, but occur more frequently than in focal nodular hyperplasia.

The diagnosis is often made using several imaging techniques (sonography, CT, MRT). Small adenomas behave sonographically isoechogenic to the surrounding healthy liver tissue. A biopsy is indicated in rare cases with an increased risk of bleeding and often only very limited information.

Possible infarction with acute abdominal pain; rarely rupture of the tumor with life-threatening bleeding (10% of cases). Malignant degeneration of an adenoma is possible and occurs in 8-13% of cases. It is therefore recommended to surgically remove an adenoma that is symptomatic or does not regress in size after discontinuation of hormone preparations.

Oral contraceptives must be discontinued. If the diameter of the HCA > 5 cm, surgical resection is recommended. If the diagnosis is confirmed, the tumour can be left in place if the tumour diameter is < 5 cm and the patient is free of symptoms. Further monitoring (size growth?) is required. Malignant transformation is rare and the long-term prognosis is good. Prog. If a liver adenoma is suspected, estrogen-containing preparations should be discontinued in any case.

1. Dhingra S et al (2014) Update on the new classification of hepatic adenomas: clinical, molecular, and pathologic characteristics. Arch Pathol Lab Med 138:1090-1097.
2. Thomeer MG et al (2014) Genotype-phenotype correlations in hepatocellular adenoma: an update of MRI findings. Diagn Interv Radiol 20:193-199.