Fetal Renal Hamartoma—a Benign Tumor to Be Distinguished From Wilms’ Tumor

Congenital mesoblastic nephroma with cystic component

“…Excretory urography generally demonstrates a simple mass effect (5). Rarely, associated renal cysts may fill with urographic contrast material R. D. GRIDER ET AL.…”

Integrated imaging of neonatal renal masses

“…Mesoblastic nephroma is a benign tumor composed primarily of connective tissue that grows be- tween intact nephrons and replaces most of the renal parenchyma [24,25]. An understanding of the pathology of mesoblastic nephroma is helpful in explaining the ultrasonographic appearance.…”

“…Histologically, the tumor is composed of spindle cells that are arranged in interlacing bundles and display varying degrees of differentiation. The bundles of spindle cells grow between intact nephrons at the interface of tumor with normal renal parenchyma [24]. Sonography shows a well-defined, intrarenal, solid mass with low-level echoes (Fig.…”

“…Although uncommon, ultrasonography may occasionally show hemorrhage and necrosis as variably sized anechoic regions [25]. It should be stressed that the most common solid renal mass of childhood, Wilms' tumor, is exceedingly rare in the neonate [24,25]. A focal neonatal renal mass, that has the ultrasonographic features of Wilms' tumor, should be considered a mesoblastic nephroma.…”

“…A focal neonatal renal mass, that has the ultrasonographic features of Wilms' tumor, should be considered a mesoblastic nephroma. The prognosis after complete surgical removal is excellent; chemotherapy and radiation therapy are neither necessary nor warranted, since they may cause significant morbidity [24].…”