A study of the cellularity and ultrastructure of congenital mesoblastic nephroma.

This study reported 10 cases of congenital mesoblastic nephroma (CMN) from Children's Hospital of Pittsburgh: five were the typical fibromatous lesion, two were the cellular variant, and three had both components. Six cases occurred in infants less than one week of age. The degree of cellularity had no correlation with patient or tumor size. Three- to 10-year follow-ups of nine patients showed neither local recurrence nor metastasis. One infant died of generalized bleeding post nephrectomy. Ultrastructural study of seven cases showed mesenchymal cells with varying degrees of fibroblastic and/or myofibroblastic differentiation.