Liver mesenchymal hamartoma

Hamartoma (von Meyenburg Complexes)
Mesenchymal and biliary hamartomas, also called von Meyenburg complexes and cholangiofibromatosis, consist of a mixture of hepatocytes, small, dilated bile ducts, and connective tissue, together with varying size cysts. These hamartomas range from solid to largely cystic circumscribed tumors, single to multiple, large or small, intrahepatic or even projecting from the liver surface. Multiple hamartomas are either uniform or random in distribution throughout the liver. A large autopsy study found these complexes in 6% of adults and 1% of children. They are more prevalent in polycystic kidney and liver disease.
Larger hamartomas are found mostly in young children. These cystic tumors are only mildly vascular. The a-fetoprotein level is not elevated with these tumors, helping distinguish them from hepatoblastomas. These hamartomas are considered to be nonneoplastic developmental ductal plate malformations and are not thought to be premalignant, although a rare cholangiocarcinoma does originate in a setting of multiple bile duct hamartomas. A double cancer—a hepatocellular carcinoma and a cholangiocarcinoma—was discovered in a 74-year-old man, with the cholangiocarcinoma arising in hamartomas; a histologic progression from hamartomatous to adenomatous and a cholangiocarcinoma was evident. Some of the larger hamartomas are palpable. Computer tomography reveals small hamartomas as multiple cysts scattered throughout the liver; they tend to be irregular in shape and
do not enhance, although some are more prominent postcontrast. They do not communicate with bile ducts. The larger ones consist of a complex mass ranging from solid to mostly cystic.
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radiology images of Liver mesenchymal hamartoma in an 8–monthold boy. Computed tomography shows a complex, mostly cystic tumor replacing most of an enlarged liver. Mild contrastenhancement was evident in the solid component.

Calcifications are not common, although an occasional one does contain peripheral calcifications. They tend to be mostly hypodense on postcontrast CT, although solid components enhance with contrast. Some septa also enhance postcontrast. Ultrasonography reveals these hamartomas to be hypoechoic. Larger ones become inhomogeneous and hyperechoic and contain acoustic shadowing. Limited MRI of these hamartomas reveals them to be hypointense on T1- and hyperintense on T2-weighted MR images.
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Radiology images of A mesenchymal hamartoma is hypointense on T1– (A) and mostly isointense on T2–weighted MRI (B). It contains a central cystic component (arrow). C: It enhances with contrast, except for the cystic component.

They are even more hyperintense on heavily T2-weighted images and are more apparent and more numerous on T2-weighted MRI and on MRCP than on T1-weighted images. They vary in enhancement postgadolinium, with some enhancing less than does normal liver tissue. Angiography reveals both hypovascular and hypervascular tumors. The imaging appearance in young children is similar to that seen with an undifferentiated embryonal cell carcinoma. In fact, some authors believe that a mesenchymal hamartoma represents a benign counterpart of an embryonal cell carcinoma.
Some intrahepatic hamartomas initially contain an enhancing rim, presumably representing compressed adjacent liver parenchyma, and superficially mimic the enhancing rim found with metastases. Hamartoma enhancement, however, does not progress centrally. The imaging differential diagnosis also includes hepatoblastoma and hepatocellular carcinoma. The presence of a cystic component in a liver tumor in children should suggest a hamartoma. Small liver cysts, not communicating with bile ducts and without renal involvement, also favor a diagnosis of hamartomas. Fine-needle aspiration of these lesions tends to be nondiagnostic, and core biopsies are needed.
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