Mesenchymal Hamartoma

Mesenchymal hamartoma is an uncommon lesion accounting for about 10% of all childhood liver tumors. It most likely represents a localized abnormality of ductal plate development that precedes birth; it is therefore usually considered a benign cystic developmental lesion rather than a true neoplasm. It occurs almost exclusively in young children (average age: 15 months) with a male to female ratio of approximately 2:1. Children typically present with progressive abdominal enlargement, and an association with polycystic kidney disease, congenital hepatic fibrosis and biliary hamartoma has been described.

Liver DoctorMesenquimal Hamartoma Liver Mri

Fig. 2a-i. Infantile hemangioendothelioma in a 3 month old girl. On respiratory gated T2-weighted (a) and T2-weighted fat-suppressed (b) TSE images, a large lesion (ar-rowsin a) with high SI is visible in the left liver lobe. Although some central areas of low SI are apparent (arrowhead), the SI for most of the lesion is relatively homogeneous and the lesion is sharply demarcated from the surrounding liver tissue. On the corresponding unenhanced Tl-weighted image (c) the lesion shows homogeneous low SI with some larger vessels in the periphery of the lesion (arrowheads) demonstrating flow void. On the dynamic study after contrast agent administration (d-g), the lesion shows strong initial peripheral enhancement with subsequent centripetal fill-ing-in. On equilibrium phase Tl-weighted (h) and Tl-weighted fat-suppressed (i) images the lesion shows almost complete filling-in. Only the central parts (arrow), which were hypointense on the T2-weighted image, appear hypointense. These areas correspond to fibroses and thromboses which are common findings in larger IHE. Additional lesions were noted in this case (images not shown),which confirmed the diagnosis

Fig. 3a-f. Infantile hemangioendothelioma. The nodule is homogeneously hyperintense compared to the adjacent liver tissue on the pre-contrast T2-weighted image (a), and is hypointense on the pre-contrast Tl-weighted image (b). Dynamic phase imaging after the administration of Gd-BOPTA reveals peripheral intense enhancement during the arterial phase (c), incomplete filling-in during the portal venous phase (d) and complete filling-in during the equilibrium phase (e). The nodule is well-defined and hypointense with central contrast agent pooling (arrow) on the delayed hepatobiliary phase image (f)

Fig. 3a-f. Infantile hemangioendothelioma. The nodule is homogeneously hyperintense compared to the adjacent liver tissue on the pre-contrast T2-weighted image (a), and is hypointense on the pre-contrast Tl-weighted image (b). Dynamic phase imaging after the administration of Gd-BOPTA reveals peripheral intense enhancement during the arterial phase (c), incomplete filling-in during the portal venous phase (d) and complete filling-in during the equilibrium phase (e). The nodule is well-defined and hypointense with central contrast agent pooling (arrow) on the delayed hepatobiliary phase image (f)

Pharmacokinetic Mri Liver

Fig. 4a-g. Focal nodular hyperplasia. A 13 year old boy presented with an unclear liver lesion on US, and had a medical history of chemotherapy and surgery for neuroblastoma. On the T2-weighted HASTE image (a), an isointense lesion (arrow) surrounded by a hypointense rim is visible in segment VII of the right liver lobe. The lesion is slightly hypointense on the corresponding T1-weighted "in-phase" image (b), and hyperintense on the T1-weighted fat-suppressed (c) and T1-weighted "out-of-phase" (d) images. Note the diffuse steatosis of the liver indicated by the reduced liver SI on the out-of-phase image due to preceding chemotherapy. On the arterial phase image (e) after administration of Gd-BOPTA (0.05 mmol/kg), the lesion shows intense hypervascularisation with depiction of a central scar. On the portal venous phase image (f), the central scar shows uptake of contrast agent; this is characteristic for FNH. This diagnosis is confirmed by the behavior of the lesion on the T1-weighted fat-suppressed image in the hepatobiliary phase, in which the lesion shows stronger contrast enhancement than the surrounding (g) liver tissue. This indicates a lesion that contains benign functioning hepatocytes and abnormal biliary drainage. This is the characteristic feature of FNH

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Fig. 5a-e. Multiple hemangioma in a case of viscerocutaneous hemangiomatosis in a newborn. The T2-weighted HASTE image (a) as well as the respiratory gated T2-weighted TSE image (b) show multiple hyperintense lesions (arrowsin a) in both liver lobes. On the corresponding unenhanced Tl-weighted image (c) the lesions are hypo- to almost isointense compared to the normal liver parenchyma. The unenhanced Tl-weighted fat-suppressed image (d) reveals multiple tortuous vessels (arrowheads) with flow void that lead to the lesions. The lesions show pooling of contrast agent in the equilibrium phase (e) after contrast agent administration, indicating vascular tumors e

On imaging studies mesenchymal hamartoma is a large, predominantly cystic mass frequently measuring 15 cm or more in diameter at the time of diagnosis. The tumors are generally well-defined and encapsulated or pedunculated. Cysts are present in 80% of cases [40].

On cut sections, mesenchymal hamartomas have either a solid appearance reflecting a mes-enchymal predominance, or a multiloculated cystic appearance reflecting a cystic predominance. His-tologically, the tumor consists of the cystic remnants of portal triads, hepatocytes and fluid-filled mesenchyma [80]. Extramedullary hematopoiesis is commonly present. Malignant transformation of mesenchymal hamartoma has not yet been reported and surgical excision is usually curative.

On US, a mesenchymal hamartoma has the appearance of a large cyst with internal septa (cystic appearance), or, less commonly, as a smaller cyst with thick septa (mesenchymal appearance).

On CT, the tumor appears as a well-defined mass with central hypodense areas and internal septa. Both solid and cystic components may be distinguished, although calcifications have not been reported. Both the septa and the solid components enhance following the administration of contrast material [80].

The MR appearance of mesenchymal hamar-toma depends on the predominance of the stro-mal and cystic components. For lesions with a stromal predominance, the signal intensity (SI) on T1-weighted images is lower than that of the normal liver, because of increased fibrosis. Conversely, if the cystic component predominates, the appearance is similar to that of other cystic masses with marked hyperintensity on T2-weighted images. Multiple septa traversing the tumor can be seen, indicating that the lesion is not a simple cyst [80].

The SI of the different locules may vary, indicating different concentrations of proteinaceous material.After the injection of contrast agent, both the mesenchymal component and the septa enhance in a manner similar to that observed on CT.

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