Hepatocellular adenoma overview

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Overview
Historical Perspective
Classification
Pathophysiology
Causes
Differentiating Hepatocellular adenoma from other Diseases
Epidemiology and Demographics
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Natural History, Complications and Prognosis
Diagnosis
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Cafer Zorkun, M.D., PhD. Zahir Ali Shaikh, MD[2]

Overview

The hepatocellular adenoma is an uncommon benign liver adenoma that is most commonly associated with oral contraceptive use in women of childbearing age. It was first described by Edmondson in 1958 as an encapsulated liver tumor that does not contain bile ducts. In 1970s several case series supported the hypothesis of an association between oral contracptives and hepatocellular adenoma. It is generally asymptomatic, the typical clinical manifestations include spontaneous rupture or hemorrhage leading to acute abdominal pain with progression to hypotension and even death. There are no specific physical examination findings associated with adenoma. The liver function tests and serum tumor markers are usually normal, but may be raised secondary to necrosis or hemorrhage and alkaline phosphatase may be raised in hepatocellular adenomatosis. Th causes of hepatocellular adenoma include; oral contraceptive medications, long term anabolic androgenic steroids, obesity, metabolic syndrome and glycogen storage diseases. It is more commonly seen in western countries where they are exposed to higher doses of oral contraceptive medications. The estimated incidence is 3 per 1,000,000/year and is 3 to 4 per 100,000 with long term oral contraceptive use. The hepatocellular adenomas are classified on the basis of molecular patterns called phenotypic genotypic classification into 04 groups including; HNF1 alpha inactivated adenoma, beta catenin activated adenoma, inflammatory hepatic adenoma and unclassified type adenoma. The exact pathogenesis of hepatocellualr adenoma is still unknown, however, its association with oral contraceptive use is well established. The other associations of adenoma include; long term use of anabolic androgenic steroids and glycogen storage diseases as well. It has been linked to mutations in HNF1a and beta catenin genes. On gross pathology, the hepatocellular adenoma appears as solitary or multiple, unencapsulated and well demarcated lesion, which can occasionally be pedunculated or encapsulated that can also form multiple masses. The intra tumoral hemorrhage can give rise to soft, necrotic, red brown lesion on gross appearance. The microscopic features of hepatocellular adenoma include benign hepatocytes arranged in mildly thickened cell plates with a preserved reticulin network and thin walled arteries. The arteries and arterioles are not accompanied by other portal tract elements such as bile ducts, portal veins or fibroconnective tissue. The hepatocellular adenoma must be differentiated from focal nodular hyperplasia, large regenerative hyperplasia, hepatocellular carcinoma in noncirrhotic patients & fibrolamellar hepatocellular carcinoma, cholangiocarcinoma and metastases. If left untreated, there is 30% bleeding risk. Complications include; bleeding, rupture and malignant transformation. The CT scan findings of heaptocellular adenoma include; non lobulated, well marginated mass that can be encapsulated and rarely calcified and heterogeneous hyperattenuating area within the tumor seen in necrosis or old hemorrhage. The MRI findings include; from hyperintense to mildly hypointense relative to the liver tissue on T1 weighted images. On T2 weighted images they are predominantly hyperintense relative to the liver, whereas in the presence of necrosis or hemorrhage they can be heterogeneous with hyper or hypoattenuating signal. The gold standard method for diagnosis of hepatocellular adenoma is excision biopsy of the liver lesions either by surgery or laparoscopically. There is no specific medical therapy for the adenoma, wait & watch policy is recommended for hepatocellualar adenomas <5 cm following cessation of oral contraceptives. Annual followup with MRI or ultrasound is recommended until menopause. Surgical resection is the treatment of choice for adenomas that are >5 cm in diameter, that increase in size, lesions with intra tumoral hemorrhage and male patients (irrespective of the adenoma size). The radiofrequency ablation (RFA) and trascathter arterial embolization (TAE) may be tried in patients who are poor candidates for surgery.

Historical Perspective

Hepatocellular adenoma was first described in 1958 by Edmondson as an encapsulated liver tumor that does not contain bile ducts. Baum reported the important relationship between the oral contraceptive use and hepatocellular adenoma development in 1973. Edmondson in 1976 published a case control study giving further evidence of this association.

Classification

The hepatocellular adenomas are classified on the basis of molecular patterns called phenotypic-genotypic classification into 04 major groups including; HNF1 alpha inactivated adenoma, beta catenin activated adenoma, inflammatory hepatic adenoma and unclassified type adenoma.

Pathophysiology

The exact pathogenesis of hepatocellular adenoma is still unknown, however, its association with oral contraceptive use is well established. It has also been associated with long term use of anabolic androgenic steroids and glycogen storage diseases. The hepatocellular adenoma have been linked to mutations in HNF1a and beta catenin genes. On gross pathology it appears as a solitary or multiple, unencapsulated and well demarcated mass lesion, which can occasionally be pedunculated or encapsulated that can also form multiple masses. The intratumoral hemorrhage can give rise to soft, necrotic, red brown lesion on gross appearance. The microscopic features of hepatocellular adenoma include benign hepatocytes arranged in mildly thickened cell plates, with a preserved reticulin network and this walled arteries. The arteries and arterioles are not accompanied by other portal tract elements such as bile ducts, portal veins or fibroconnective tissue.

Causes

The causes of hepatocellular adenoma include; oral contraceptive medications, pregnancy, long term use of anabolic androgenic steroids, maturity onset diabetes of young, metabolic syndrome, obesity, glycogen storage diseases, clomiphene and vascular disorders like portal vein agenesis, budd chiari syndrome and hereditary hemorrhagic telangiectasia.

Epidemiology and Demographics

The incidence of hepatic adenoma is approximately 3 per 100,000 individuals worldwide.

Risk factors

The most potent risk factor in the development of hepatocellular adenoma is use of oral contraceptive pills.

Screening

According to the American Association for the Study of Liver Diseases and United States Preventive Services Task Force, there is insufficient evidence to recommend routine screening for hepatocellular adenoma.

Differentiating Hepatocellular adenoma from other Diseases

Hepatocellular adenoma must be differentiated from other diseases such as hepatocellular carcinoma, focal nodular hyperplasia, liver metastases (hypervascular), haemangioma of the liver, fibrolamellar hepatocellular carcinoma.

Natural History, Complications and Prognosis

If left untreated, 30% of patients with hepatocellular adenoma may progress to develop risk of bleeding.Common complication of Hepatocellular adenoma includes spontaneous rupture, haemorrhage and malignant transformation to Hepatocellular carcinoma.

Diagnosis

History and Symptoms

Hepatocellular adenoma can present as right upper quadrant abdominal pain, acute abdomen or life threatening bleeding.

Physical Examination

Laboratory Findings

An elevated concentration of serum alkaline phosphatase and gamma glutamyl transferase may be present in patients with Hepatocellular adenoma.

Chest X Ray

There are no chest x-ray findings associated with hepatocellular adenoma.

CT

MRI

Ultrasound

Other Imaging Findings

Other Diagnostic Studies

Treatment

Medical Therapy

Surgery

All hepatocellular adenoma should be surgically resected, because of the risk of rupture causing bleeding and because they may contain malignant foci.

Primary Prevention

Secondary Prevention

References

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