Undifferentiated (Embryonal) Sarcoma of the Liver

Undifferentiated (embryonal) sarcoma of the liver is the fourth or fifth most common liver tumor in children. It may or may not share the same histiogenesis as mesenchymal hamartoma, with the two representing the ends of a spectrum.

CT and MR findings can resemble those of a cystic lesion, possibly related to the abundant myxoid stroma, leading to misdiagnosis as a hydatid cyst or amebic abscess. US is useful in demonstrating the solid nature of the tumor.

Suggestive findings include a large hepatic lesion with a seemingly cystic appearance on CT and MR images and a largely solid appearance on US images. The tumors demonstrate predominantly low T1 and high T2 signal. Areas of hemorrhage appear as T1 hyperintensity and increased attenuation on CT. Post-contrast images reveal enhancing internal nodules.

On ultrasound, our case demonstrates a large, predominantly solid lesion within the liver with small cystic spaces and no significant vascularity. CT shows a large, predominantly low-attenuation lesion within the right lobe of the liver, with several internal septa and areas of increased. No definite enhancement was seen. On MRI, the lesion is predominantly T1-hypointense and T2-hyperintense with nodular enhancement superiorly.

The differential diagnosis for a cystic lesion in the liver (based on its appearance on CT and MR) includes biliary cystadenoma and cystadenocarcinoma, cystic degeneration of hepatocellular carcinoma, infection (abscess, bacterial and parasitic), metastatic disease, and resolving hematoma.

References

• Buetow PC, Buck JL, Pantongrag-Brown L, Marshall WH, Ros PR, Levine MS, Goodman ZD. Undifferentiated (embryonal) sarcoma of the liver: pathologic basis of imaging findings in 28 cases. Radiology. 1997 Jun;203(3):779-83.
• Crider MH, Hoggard E, Manivel JC. Undifferentiated (embryonal) sarcoma of the liver. Radiographics. 2009 Oct;29(6):1665-8.
• Shehata B, Gupta NA, Katzenstein H, Steelman CK, Wulkan ML, Gow KW, Bridge JA, Kenney BD, Thompson KS, de Chadarevian JP, Abramowsky CR. Undifferentiated embryonal sarcoma of the liver is associated with mesenchymal hamartoma and multiple chromosomal abnormalities: a review of eleven cases. Pediatr Dev Pathol. Epub 2010 Oct 6.