intralobar nephrogenic rests

Intralobar nephrogenic rests (ILNRs) are precursor lesions for Wilms tumours and are associated with WT1 gene mutations.

ILNR-Wilms tumour sequence

ILNR-associated Wilms tumours have a co-clustering of WT1 and Beta-catenin (CTNNB1) mutations and unique histological features characterised by a stromal-predominant histology. (17172473)

CTNNB1 mutation is a later event in Wilms tumorigenesis and CTNNB1 mutations might be associated with rhabdomyogenesis. (17172473)

See also

 CTNNB1
 Wilms tumor

Beckwith classification (1990)

A new classification and terminology is proposed for precursor lesions of Wilms’ tumor (WT), based upon morphology and natural history.

The generic term nephrogenic rest (NR) is used for all WT precursors. Two major categories of NR are recognized: perilobar (PLNR) and intralobar (ILNR).

Nephroblastomatosis signifies the presence of multiple or diffuse NRs.

Nephroblastomatosis can be classified into four categories:
 (a) perilobar (PLNR only);
 (b) intralobar (ILNR only;
 (c) combined (PLNR and ILNR);
 (d) universal.

The individual rests can be subdivided into:
 (a) nascent or dormant NRs;
 (b) maturing or sclerosing NRs;
 (c) hyperplastic NRs;
 (d) neoplastic NRs.

Of 282 evaluable unilateral WT specimens, 28.4% were definitely rest-positive, and an additional 12.4% were probably positive, with equal prevalence of PLNRs and ILNRs.

Median age at diagnosis of WT was 36 months with PLNRs, 16 months with ILNRs, and 12 months if both types were present.

PLNRs were strongly associated with synchronous bilateral WTs, and ILNRs with metachronous contralateral WTs.

ILNRs were associated with aniridia and Drash syndrome, whereas PLNRs were more commonly found with hemihypertrophy and/or Beckwith-Wiedemann syndrome.

The delineation of two distinct categories of WT precursors suggests pathogenetic heterogeneity for WTs.

References

 Single-nucleotide polymorphism in WT1 gene in a hyperplastic intralobar nephrogenic rest with botryoid protrusion. Mizuno K, Hayashi Y, Tozawa K, Iwatsuki S, Kojima Y, Kohri K. Urology. 2010 Jul;76(1):149-52. PMID: 19914700

 Sequential WT1 and CTNNB1 mutations and alterations of beta-catenin localisation in intralobar nephrogenic rests and associated Wilms tumours. Fukuzawa R, Heathcott RW, More HE, Reeve AE. J Clin Pathol. 2006 Dec 15; PMID: 17172473

 Nephrogenic rests, nephroblastomatosis, and the pathogenesis of Wilms’ tumor. Beckwith JB, Kiviat NB, Bonadio JF. Pediatr Pathol. 1990;10(1-2):1-36. Review. PMID: 2156243