Undifferentiated (embryonal) sarcoma of the liver: Pathologic basis of imaging findings in 28 cases

PURPOSE: To correlate the imaging and pathologic features of undifferentiated (embryonal) sarcoma (UES) and account for the discrepancy between the solid appearance at ultrasound (US) and the almost cystlike appearance at computed tomography (CT) and magnetic resonance (MR) imaging. MATERIALS AND METHODS: The clinical, pathologic, and imaging findings in 28 patients (age range, 3-49 years) with pathologically proved UES were retrospectively reviewed. All patients underwent at least one cross-sectional imaging study to include CT (27 patients), US (21 patients), and MR imaging (six patients). Tumor size, gross morphology (n = 27), histologic features, and proportion of solid and cystlike components were evaluated and correlated to the imaging findings. RESULTS: The mean transverse diameter of the tumors was 14 cm (range, 10-25 cm). At gross examination, the tumors were predominantly solid (mean, 83% of tumor volume), and pathologic and US findings were concordant. Conversely, CT scans showed low attenuation (approximately that of water) in 88% of the tumor volume and T2-weighted MR images showed high signal intensity (approximately equal to that of cerebrospinal fluid) in 89% of the tumor volume. CONCLUSION: UES shows a misleading cystlike appearance at CT and MR imaging compared with US and pathologic findings. In a child or young adult with a liver tumor, this finding is useful in making a prospective diagnosis and avoiding misguided attempts at drainage.