Congenital Mesoblastic Nephroma: A Rare Neoplasm of The Newborn

Congenital mesoblastic nephroma (CMSN) is the most common renal neoplasm in the first trimester of the neonatal period (1). The tumor was first described as renal tumor of infancy by Bolande et al. in 1967 and histologically divided into classical, mixed and cellular subtypes (2). The tumor is usually surrounded by renal capsule and the tumor-renal parenchyma border is irregular. It shows a growth pattern spreading to the renal parenchyma and infiltrating the perirenal adipose tissue (3,4). The tumor has a myomatous appearance and has a rubbery consistency. Classic or typical congenital mesoblastic nephroma (or fibromatous type) (1/3) is usually seen before the first 3 months of life and has a benign course.