Mesoblastic nephroma in an adult patient: recurrence 21 years after removal of the primary lesion.

A histologically benign mesoblastic nephroma was diagnosed in a 19-year-old girl. The tumor was resected but recurred, invading the liver 21 years after the removal of the primary lesion. The recurrent tumor was composed of fibroblastic cells surrounded by collagen and elastin-rich interstitial material. Some tumor cells also contained fibrillar bodies, most likely representing extracellular material packaged for secretion.