Primary malignant tumor of liver composed of primitive mesenchymal cells with partial, divergent differentiation
IMAGING
• Large, encapsulated, spherical mass
• May have peripheral rim of viable, hypervascular tumor
• Often has large complex, cystic spaces with focal hemorrhage
• May show signs of vascular invasion
Hepatic, portal vein, or inferior vena cava (IVC) invasion
• Large subcapsular tumors may rupture
• Nodal or distant metastases are common
Lung and osseous mets are most common
TOP DIFFERENTIAL DIAGNOSES
• Metastases and lymphoma, hepatic
• Hydatid (echinococcal) disease
• Angiosarcoma, liver
CLINICAL ISSUES
• Majority of patients are children (ages 6-10)
• Comprises 6-13% of primary hepatic neoplasms in children
• Rare reports in adults of all ages
• Generally grim prognosis; 5-year survival averages ∼ 15%
• Resection ± adjuvant or neoadjuvant therapy have recently improved prognosis
DIAGNOSTIC CHECKLIST
• Check for primary extrahepatic tumor
• Metastases are much more common cause of complex cystic hepatic tumors
(Left) Axial T2WI MR in a 57-year-old woman shows a huge hepatic mass that replaces most of the right lobe. The mass is heterogeneously hyperintense, though not as bright as another lesion that proved to be a cavernous hemangioma.
(Right) Axial T1WI C+ MR in the same case shows nodular peripheral enhancement of the hemangioma , whereas most of the sarcoma shows no enhancement. The tumor is an undifferentiated sarcoma, which is largely necrotic and hemorrhagic as suggested by MR.
(Left) Axial arterial phase CECT in a 73-year-old man shows a large, encapsulated mass that has central necrosis and a periphery of hypervascular solid tumor, a common feature of sarcomas in general, though not specific for a primary hepatic sarcoma.
(Right) Coronal CT reconstruction in the same case shows the large, centrally necrotic hepatic sarcoma . Absence of immunohistochemical evidence of muscle, epithelial, or vascular differentiation led to the final diagnosis of undifferentiated sarcoma.
TERMINOLOGY
Synonyms
• Undifferentiated embryonal sarcoma
• Malignant mesenchymoma
Definitions
• Primary malignant tumor of liver composed of primitive mesenchymal cells with partial, divergent differentiation
IMAGING
General Features
• Best diagnostic clue
Large, spherical, encapsulated necrotic or complex cystic mass
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that replaces most of the right lobe. The mass is heterogeneously hyperintense, though not as bright as another lesion 
that proved to be a cavernous hemangioma.
, whereas most of the sarcoma 
shows no enhancement. The tumor is an undifferentiated sarcoma, which is largely necrotic and hemorrhagic as suggested by MR.
that has central necrosis and a periphery of hypervascular solid tumor, a common feature of sarcomas in general, though not specific for a primary hepatic sarcoma.
. Absence of immunohistochemical evidence of muscle, epithelial, or vascular differentiation led to the final diagnosis of undifferentiated sarcoma.
