Nonmyxoid mediastinal lipoblastoma in a 2-year-old girl: Case report with US, CT, and MRI findings.

Lipoblastomas are rare, benign tumors of mesenchymal origin that contain adipose tissue. They usually develop in the soft tissues of an extremity in infants, children, and young adolescents. We report the case of a 22-month old girl referred to our staff for swelling in the supraclavicular fossa, which was observed when the child cried. The ulstrasonographic examination revealed a mass in the anterosuperior portion of the mediastinum that extended into the right supraclacular fossa. The lesion was weakly hyperechoic with clear-cut margins and did not appear to invade surrounding tissues. On CT, it appeared inhomogeneously hypodense with denitometric characteristics of adipose tissue. On MRI, it was hyperintense on both T1- and T2-weighted sequences and reduced signal intensity in FAT SAT sequences. In light of the imaging features and predominant adipose tissue component, the mass was diagnosed as a mediastinal lipoblastoma, and this diagnosis was confirmed by surgical histology.