Extrarenal rhabdoid tumours outside the central nervous system in infancy.

Background: Malignant rhabdoid tumours (RT) are increasingly recognized in young children, probably as a consequence of advances in accurate histological diagnosis rather than a true increase in frequency. Although typically presenting as renal tumours in infancy, extrarenal tumours outside the central nervous system (CNS) in children less than 12 months of age are now well recognized, but previous literature on their imaging features is very limited.

Objective: To demonstrate the imaging features of extrarenal RTs outside the CNS.

Materials And Methods: A retrospective database review was made from 1989 to 2007 of patients diagnosed with extrarenal RT in infancy, i.e. below 12 months of age.

Results: There were nine patients (six boys and three girls). The age at presentation varied from 1 to 11 months (average 6 months). Tumours were located in the thorax/mediastinum (n=3), liver (n=3), neck (n=1), shoulder (n=1) and axilla (n=1). The imaging modalities used included US (n=8), CT (n=7) and MRI (n=6). Bone scan was positive in one patient, while metastases at the time of diagnosis occurred in four patients. On MRI the tumours tended to show nonspecific hypointensity on T1-W images and heterogeneous hyperintensity on T2-W images, with heterogeneous enhancement.

Conclusion: This is the largest radiological series of extrarenal RTs outside the CNS in infancy. In our series no imaging features were found specific to the diagnosis. A tendency towards large size and mediastinal/paravertebral location were noted. A hypodense solid component on CT and a heterogeneous hyperintensity on T2-W MR images suggest that this tumour should be considered in the routine differential diagnosis of soft-tissue tumours in infancy, in addition to rhabdomyosarcoma.