Nephroblastoma with associated aortic rupture in a rat.

A nephroblastoma was diagnosed in a 6-month-old, male rat which died unexpectedly. The right kidney was replaced by a large, white, irregularly shaped mass. Microscopically, the mass consisted of an embryonic blastema showing epithelial differentiation into immature tubules and glomeruloid structures. An aortic aneurysm and aortic rupture were present within the thoracic cavity. It was suspected that the aortic rupture was secondary to hypertension mediated through the renin-angiotensin system.