Unusual mesoblastic nephroma in a young child.

We report a 1-year 11-month-old girl demonstrating a large renal mass with a unique presentation on imaging (US, CT and plain radiography), pathology and histology. The imaging features did not correspond with a Wilms' tumour, the most commonly found renal tumour in the child of this age. The US and CT findings resembled a benign lesion with an unusually high fat content. Histological evaluation demonstrated a congenital mesoblastic nephroma, a tumour entity typical for the neonatal period or early infancy, with an additional unusual, predominantly lipomatous differentiation.