Intralobar nephroblastematosis in a nine-week-old Wistar rat

Area of Science:

• Veterinary Pathology
• Developmental Biology
• Toxicology

Background:

• Intralobar nephroblastematosis (ILNB) is recognized as a precursor lesion to nephroblastoma (NB) in rodent models.
• Understanding ILNB is crucial for interpreting renal lesions in toxicology studies and their relevance to human pediatric kidney development.

Observation:

• A unilateral ILNB lesion was identified in the kidney of a nine-week-old female Wistar rat during a short-term toxicity study.
• The lesion was microscopic, unencapsulated, and composed of basophilic blastemal cell sheets with moderate differentiation into rosettes, primitive tubules, and glomeruloid structures.
• Compressed renal tubules and eosinophilic/basophilic secretions within primitive tubules were noted, but clinical pathology showed no altered renal function.

Findings:

• The blastemal cells expanded interstitially, trapping and compressing adjacent renal tubules.
• Differentiation of blastemal cells into primitive tubular and glomeruloid structures was observed.
• The lesion's morphology was compared against criteria for renal dysplasia, nephrogenic rest, and nephroblastoma in rats and humans.

Implications:

• This case provides a detailed morphological description of ILNB in a Wistar rat, contributing to the understanding of rat kidney development and potential toxicological effects.
• Comparing the rat lesion with human counterparts aids in the interspecies extrapolation of findings from preclinical toxicology studies.
• The findings highlight the importance of recognizing precursor lesions like ILNB in non-neoplastic findings during animal studies.