Which histologic findings are characteristic of hepatocellular adenoma (HCA)?

Updated: Feb 21, 2018
  • Author: Bradford A Whitmer, DO; Chief Editor: BS Anand, MD  more...
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Answer

Upon gross examination, hepatocellular adenomas appear as sharply circumscribed, light brown to yellow tumors that are soft in consistency and often lack a true fibrous tumor capsule. [52] Although these lesions are usually solitary, hepatocellular adenomas may be multiple, with sizes ranging from 1 to 30 cm, although most are between 8 and 15 cm. Adenomas tend to be larger in women on OCPs. They also occur more frequently in the right lobe and are usually subcapsular, although pedunculated adenomas have also been described.

On microscopic examination, the hallmark of adenomas is the normal appearance of the hepatocytes. These are arranged in sheets and have no malignant features. These cells tend to be larger than normal hepatocytes, and their cytoplasm often contains fat or glycogen. (Their cytoplasm may appear relatively pale due to abundant glycogen stores when compared with normal hepatocytes). Generally, few, if any, portal tracts are present, and no central veins or bile ducts should be present. [53] However, Bisceglia et al reported that subtypes of HAs may have CK7 positive ductules and are called hepatocellular adenoma with ductal/ductular differentiation. [54]

Peliosis hepatis may occasionally be seen, and Kupffer cells are reduced in number or are absent. [55] Vessels, when observed, tend to have thickened walls. Areas of thrombosis and infarction may be observed. Most hepatocellular adenomas contain a variable degree of microscopic collections of fat. Differentiation from a high-grade HCC can be difficult, if not impossible. Adenomas tend to lack malignant-appearing mitotic structures, the cell plates are generally only 2 cells thick, and no cellular infiltration (invasion) into the capsule or surrounding liver parenchyma occurs. Unfortunately, these features may also be seen in HCC, especially if it is well differentiated.

Hypervascularity is present upon the surface of the lesion. Because adenomas contain no portal vein branches, their blood supply is entirely arterial. The tendency for these lesions to bleed may be related to poor connective tissue support and their increased vasculature, which is made up of thin-walled, dilated sinusoids carrying blood at arterial pressure.


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