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Kidney tumor - cysts, children, adult benign

Childhood neoplasms

Nephroblastomatosis / nephrogenic rests


Reviewers: Mandolin Ziadie, M.D. (see Reviewers page)
Revised: 30 December 2011, last major update December 2011
Copyright: (c) 2003-2011, PathologyOutlines.com, Inc.

General
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Nephrogenic rests: persistent foci of embryonal cells seen after the period of normal nephrogenesis
Nephroblastomatosis: multifocal or diffuse nephrogenic rests
● May be intralobar or perilobar

Epidemiology
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● 1% of neonatal kidneys; florid cases associated with congenital anomalies and hypertension
Intralobar rests have an increased rate of progression to Wilms’ tumor, are more commonly associated with WT1 mutations, Denys-Drash syndrome and WAGR syndrome
Perilobar rests are seen in sporadic tumors and are associated with genetic / epigenetic dysregulation at 11p15 (Clin Cancer Res 2008;14:7635), idiopathic hemihypertrophy and Beckwith-Wiedemann syndrome

Clinical features
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● Precursor lesions of Wilms’ tumor, seen in 30–44% of kidneys resected for Wilms’ tumor (WT)

Case reports
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● Male newborn death with bilateral nephroblastomatosis (Arch Pathol Lab Med 1989;113:729)
● Newborn with lumbosacral ectopic rest (Am J Surg Pathol 2004;28:1389)
● Siblings with universal nephroblastomatosis with nephromegaly (Pediatr Dev Pathol 2009;12:47)

Treatment
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● Conservative

Gross description
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● May be inapparent on gross examination or appear as nodules / foci of capsular thickening / scar beneath the capsule or in the deep cortex / medulla

Gross images
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Perilobar nephrogenic nests

Micro description
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● Tightly packed nests or diffuse sheets of primitive but non-anaplastic blastemal / primitive epithelial cells with scanty stroma
● No cartilage or primitive mesenchyme
● May have a sclerosing or hyperplastic pattern
Intralobar: randomly distributed throughout cortex and medulla with irregular margins, more stroma than blastema or tubules
Perilobar: peripheral with sharply demarcated margins, composed of blastema and tubules with scanty or sclerotic stroma, often solitary

Micro images
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Intralobar:

Small interstitial lesion mixed with normal nephronic elements


Mature and immature elements throughout renal parenchyma


Sclerosing intralobar nephrogenic rest with mature spindle cell stroma and a few residual blastemal islands, may resemble focal renal dysplasia


Neoplastic intralobar rest


Mature and immature elements are intermingled throughout the renal parenchyma

Perilobar:
   

Microscopic rests composed of blastemal cells, are termed "incipient" in neonates and "dormant" otherwise


Sclerosing perilobar nephrogenic rest


Focal scarring


Hyperplastic perilobar rest in sclerosing stage


Multifocal hyperplastic perilobar rests

   

Nearly confluent rind of perilobar rest tissue; thick rind of perilobar tissue

   

Neoplastic perilobar rest

Differential diagnosis
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Wilms’ tumor

Additional references
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Adv Anat Pathol 2001;8:276

End of Kidney tumor - cysts, children, adult benign > Childhood neoplasms > Nephroblastomatosis / nephrogenic rests


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