Congenital nephroblastoma in a Holstein-Friesian fetus - case report.

A seven-year-old Holstein-Friesian cow was brought to the hospital with signs of dystocia in the eighth month of gestation. The dystocia was relieved and a dead male fetus removed. The fetus had a significantly distended abdomen. At necropsy, the fetus showed a very large, round and well encapsulated extra renal mass in the abdominal cavity. The cut surfaces of the mass showed a white, cauliflower-like growth with red surfaces. The lobules were spongy and distinctly demarcated by fat and hemorrhages. Microscopic examination of the tissue sections revealed blastemal, epithelial and mesenchymal elements. These cells were round to oval in shape with scanty cytoplasm. The nuclei were spherical, sometimes vesicular and hyperchromatic. The epithelial structures resembled the development of tubulo-glomerulogenesis. The mesenchymal cells were polyhedral in shape, found between the tubules. The gross and microscopic features of the tissue sections were consistent with a diagnosis of nephroblastoma.