Nephrogenic rests are abnormally per­ sistent foci of embryonal cells (still pre­ sent after 36 weeks of gestation) that are potentially capable of developing into nephroblastoma (also called Wilms tumour). The presence of diffuse or multifocal nephrogenic rests is called nephroblastomatosis.

Nephrogenic rests are found in 25-40% of patients with nephroblastoma, and in approximately 1% of term infant autop­sies.

Nephrogenic rests can be found adjacent to nephroblastoma or in the surrounding renal parenchyma. They are classified into perilobar and intralobar types.

Here are 5 differences between perilobar and intralobar nephrogenic rests.

1. LOCATION

Perilobar nephrogenic rests are peripherally located, wheras intralobar nephrogenic rests are randomly intermingled between the renal parenchyma, typically located in the central areas of the lobe.

2. DEMARCATION FROM ADJACENT PARENCHYMA

Perilobar nephrogenic rests are sharply demarcated from the surrounding tissue, whereas intralobar nephrogenic rests are poorly de­marcated, usually infiltrate among native nephrons.

3. STROMA

Perilobar nephrogenic rests have scanty stroma, whereas intralobar nephrogenic rests are and are composed mainly of stromal and epithelial elements.

4. FOCALITY

Perilobar nephrogenic rests are usually multifocal whereas, intralobar nephrogenic rests are mostly unifocal (often single).

5. ASSOCIATED CONDITIONS

Perilobar nephrogenic rests are associated with hemihypertrophy and overgrowth syndromes such as Beckwith-Wiede­mann syndrome. lntralobar nephrogenic rests are associated with Denys-Drash syndrome (which is associated with nephroblastoma, pseudohermaphrodit­ ism, glomerulopathy, and renal failure) and WAGR syndrome (Wilms tumour / nephroblastoma, aniridia, genitourinary anomalies, and mental retardation syn­drome).