Ossifying renal tumor of infancy.

A renal ossifying tumor of infancy is a rare event with few cases having been published, and the etiology has not yet been established. We report on two new cases of this unusual neoplasm. A 2-year-old boy presented with intermittent painless gross hematuria. After several diagnostic procedures, an open pyelolithotomy was performed and the histological diagnosis of renal tumor of infancy was finally made. The history of the second case is very similar. An 8-week-old infant presented with gross hematuria. As in the first case, an open pyelolithotomy was performed and a tumor entirely covered with blood clots was found in the renal pelvis and completely removed. A histological diagnosis of renal ossifying tumor of infancy was made. Using the literature available, the histological criteria and biological behavior are discussed, together with the diagnostic and therapeutic algorithm for this tumor. In infants with gross hematuria and a calcified (non-)invasive mass in the pelvi-calceal system, renal ossifying tumor should be considered in the differential diagnosis. MRI or CT scan offers a good diagnostic guide.